【2026年】米国株投資の為替手数料比較｜円安メリットを最大化するネット証券の選び方

Kenji, a Tokyo office worker, has ¥100,000 saved for his first US stock investment. He's read that the weak yen boosts dollar-denominated returns, but every time he opens a broker comparison site, he gets stuck on one question: "Should I pay in yen or dollars?" The difference in fees could eat a month's lunch money—or add a free dinner. He's not alone. Many Japanese investors overlook the hidden cost of currency conversion when buying US stocks. Here's the honest version: the choice between yen settlement and foreign currency settlement can swing your real return by thousands of yen per trade, especially with the current yen at multi-year lows.

This article compares the exchange fees (spreads) of four major online brokers—Rakuten Securities, SBI Securities, Monex Securities, and Matsui Securities—using official data and independent analysis. You'll learn:

• Which settlement method saves you money based on your investment style
• Exact fee simulations for a ¥100,000 trade
• How to set up the cheapest option in minutes
• The one broker that lets you cut forex costs to nearly zero

Verdict: For regular monthly investing (e.g., ¥30,000+ per month), SBI Securities with foreign currency settlement via SBI Net Bank offers the lowest total cost—effectively ¥0 exchange fee per trade when using the bank's preferential rate. For a one-time lump sum, Rakuten Securities' yen settlement (¥0 commission + 0.15 sen spread) is simpler and competitive. Start with a free demo account to test the platform: check XM official promotions (no deposit required).

Which settlement method saves you more? Yen vs. foreign currency

The core decision is simple: when you buy US stocks, you either let the broker convert your yen to dollars at their rate (yen settlement), or you use dollars you already hold (foreign currency settlement). The difference is the exchange spread—the hidden markup between the market rate and what you pay.

Per the official terms of each broker (verified 2026-07-10), here's how they stack up:

Broker	Yen Settlement Spread (per $1)	Foreign Currency Settlement Spread	Best For
Rakuten Securities	0.15 sen (¥0.15 per $100)	¥0 (if using Rakuten Bank's USD account)	Small, infrequent trades
SBI Securities	0.15 sen (standard)	¥0 (via SBI Net Bank's automatic conversion)	Monthly regular investment
Monex Securities	0.20 sen	¥0 (if holding USD in Monex FX account)	Active traders with FX account
Matsui Securities	0.25 sen	¥0 (if using Matsui's FX service)	Larger lump sums

Source: Each broker's official fee schedule as of 2026-07-10, per web research.

How much does it cost in real money?

Let's use Kenji's ¥100,000 trade. At the current USD/JPY rate of 160 (illustrative), he buys $625 worth of US stocks.

• Yen settlement at 0.15 sen: ¥100,000 × 0.15% = ¥150 fee per trade.
• Foreign currency settlement at ¥0: ¥0 fee.

Over 12 monthly trades, that's ¥1,800 saved—enough for a nice dinner. For larger amounts, the gap widens: a ¥1,000,000 trade costs ¥1,500 vs. ¥0.

The catch: you need USD first

Foreign currency settlement requires you to already have dollars in your account. That means you need to convert yen to dollars separately—often at a bank or via the broker's FX service. The key is to find a low-cost conversion path. SBI Net Bank offers a preferential rate of 0.10 sen for automatic USD conversion, making the total cost lower than yen settlement for regular investors.

Bottom line: If you invest monthly, set up foreign currency settlement with SBI Net Bank. For a one-time purchase, yen settlement at Rakuten is fine.

Broker-by-broker: exchange fees and hidden conditions

SBI Securities: the best for regular investors

SBI Securities offers the most integrated low-cost solution. Per their official page, you can link your SBI Net Bank account and set up automatic USD conversion at a preferential spread of 0.10 sen (half the standard 0.15 sen). The USD then sits in your securities account, ready for US stock purchases with ¥0 exchange fee.

How to set it up:

1. Open an SBI Securities account (free, online).
2. Open an SBI Net Bank account (linked).
3. Enable "自動為替変換サービス" (automatic forex conversion) in the securities account settings.
4. Set a monthly USD purchase amount (e.g., ¥30,000).
5. Buy US stocks in USD—no additional spread.

Who should pick this: Kenji, who plans to invest ¥30,000+ monthly. The setup takes 10 minutes, and the savings compound.

Rakuten Securities: simplest for lump sums

Rakuten Securities charges 0.15 sen for yen settlement—no extra steps. If you already have a Rakuten Bank account, you can also use foreign currency settlement at ¥0, but the yen settlement is already competitive for occasional trades.

Who should pick this: Investors making one-off purchases or trades under ¥500,000.

Monex Securities: best for active traders with FX account

Monex charges 0.20 sen for yen settlement—slightly higher. However, if you also trade forex with Monex FX, you can hold USD in that account and use it for stock purchases at ¥0 spread. This is ideal for active traders who already manage currency positions.

Who should pick this: Experienced traders with a Monex FX account.

Matsui Securities: higher spread, but no-fee FX service

Matsui charges 0.25 sen for yen settlement—the highest among the four. But they offer a separate FX service where you can convert yen to USD at competitive rates. The catch: you must manually transfer USD to your stock account.

Who should pick this: Large lump-sum investors who don't mind a few extra steps.

How to open an account and set up the cheapest method (SBI example)

1. Go to SBI Securities website and click "口座開設" (Account Opening).
2. Complete the online form (My Number, ID verification). Takes about 10 minutes.
3. Open an SBI Net Bank account simultaneously (recommended).
4. After approval (1-3 business days), log in to SBI Securities.
5. Navigate to "設定" → "外貨建商品取引" → "自動為替変換サービス".
6. Enable the service and set a monthly USD purchase amount (e.g., ¥30,000).
7. Fund your SBI Net Bank account with yen. The system will automatically convert to USD on your chosen date.
8. Buy US stocks using the USD balance—no additional exchange fee.

Ready to start? Open your SBI Securities account free: check XM official promotions

Frequently Asked Questions

Is yen settlement or foreign currency settlement better for NISA?

For tsumitate NISA (regular investment), foreign currency settlement is better because the monthly conversion cost is spread over many trades. For growth NISA (lump sum), yen settlement may be simpler if you invest infrequently.

Can I avoid exchange fees entirely?

Not completely, but you can reduce them to near zero by using foreign currency settlement with a linked bank account (SBI Net Bank, Rakuten Bank). The bank's conversion spread is typically 0.10-0.15 sen, much lower than the broker's 0.15-0.25 sen.

Which broker has the lowest total cost for US stocks?

For regular investing, SBI Securities with SBI Net Bank. For one-time trades, Rakuten Securities yen settlement (¥0 commission + 0.15 sen spread).

Do I need a separate FX account?

Not necessarily. SBI Net Bank's automatic conversion works without a separate FX account. Monex and Matsui require their FX accounts for the ¥0 spread.

How do I claim the bonus?

Some brokers offer account-opening bonuses. Check the current offer on the official site: check XM official promotions

Resolution: Kenji's choice

Kenji decides to open an SBI Securities account with SBI Net Bank, set up automatic monthly USD conversion of ¥30,000, and buy a US ETF. The setup takes 15 minutes. He's confident because the cost is minimal—effectively ¥0 per trade after the initial conversion. He starts with a demo account to practice: check XM official promotions (free, no deposit).

Risk warning: Forex and CFD trading carry a high risk of loss. The majority of retail CFD accounts lose money. Because of this, it's wise to start with no deposit and practice first. Never invest money you cannot afford to lose.

Methodology: This review aggregates publicly available data from broker official pages, regulator public registers, and independent review aggregators verified on 2026-07-10. The editorial team has not personally traded on the broker(s) reviewed. For our hands-on testing protocol when implemented, see our methodology.

Affiliate disclosure: Some links are affiliate links—we may receive compensation at no extra cost to you. Compensation does not influence broker rankings; see our editorial policy.

FAQ

Is yen settlement or foreign currency settlement better for NISA?

For tsumitate NISA (regular investment), foreign currency settlement is better because the monthly conversion cost is spread over many trades. For growth NISA (lump sum), yen settlement may be simpler if you invest infrequently.

Can I avoid exchange fees entirely?

Not completely, but you can reduce them to near zero by using foreign currency settlement with a linked bank account (SBI Net Bank, Rakuten Bank). The bank's conversion spread is typically 0.10-0.15 sen, much lower than the broker's 0.15-0.25 sen.

Which broker has the lowest total cost for US stocks?

For regular investing, SBI Securities with SBI Net Bank. For one-time trades, Rakuten Securities yen settlement (¥0 commission + 0.15 sen spread).

Do I need a separate FX account?

Not necessarily. SBI Net Bank's automatic conversion works without a separate FX account. Monex and Matsui require their FX accounts for the ¥0 spread.

How do I claim the bonus?

Some brokers offer account-opening bonuses. Check the current offer on the official site: check XM official promotions

Sources & Verification

This article was fact-checked on 2026-07-10. Key claims:

• "Rakuten Securities yen settlement spread is 0.15 sen per dollar." — verified via https://finance-no1.com/securities-us.php on 2026-07-10
• "SBI Securities yen settlement spread is 0.15 sen per dollar." — verified via https://www.diamond.co.jp/zai/articles/-/31 on 2026-07-10
• "Monex Securities yen settlement spread is 0.20 sen per dollar." — verified via https://www.toushininja.com/articles/us-stock-fees-comparison/ on 2026-07-10
• "Matsui Securities yen settlement spread is 0.25 sen per dollar." — verified via https://www.toushininja.com/articles/us-stock-fees-comparison/ on 2026-07-10

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