How to Say "Must Not" and "Not Allowed" in Korean: ~(으)면 안 돼요

You've learned how to say what you have to do (~아/어야 해요) and what you're allowed to do (~아/어도 돼요).

Now the third piece: ~(으)면 안 돼요 - how to say what you must not do, what's not allowed, or what won't work.

Together, these three patterns form the core of Korean obligation and permission - and getting them straight is one of the most important steps at A2 level.

What Does ~(으)면 안 돼요 Mean?

Literally, (으)면 means "if" and 안 돼요 means "it doesn't work / it's not okay." So the pattern is saying: "If [you do this], it's not okay."

여기에서 사진을 찍으면 안 돼요. You must not take photos here.

늦으면 안 돼요. You can't be late. / Being late won't do.

How to Form ~(으)면 안 돼요

💡 Unlike ~(으)ㄹ 수 있다 and ~(으)ㄹ 거예요 where ㄹ drops before certain endings, in ~(으)면 the ㄹ stays: 살다 → 살면 안 돼요 ✅ (not 사면)

Conjugation Table

~(으)면 안 돼요 in Real Sentences

🚫 Rules & Prohibitions

여기에서 담배를 피우면 안 돼요.

• Literal: Here [at] cigarette [object] smoke if not okay
• Natural: You must not smoke here.

도서관에서 음식을 먹으면 안 돼요.

• Natural: You must not eat food in the library.

이 버튼을 누르면 안 돼요.

• Natural: You must not press this button.

박물관에서 사진을 찍으면 안 돼요.

• Natural: You must not take photos in the museum.

전시물을 만지면 안 돼요.

• Natural: You must not touch the exhibits.

⏰ Time & Deadlines

절대 늦으면 안 돼요. 중요한 면접이에요.

• Natural: You absolutely cannot be late. It's an important interview.

마감을 놓치면 안 돼요.

• Natural: You must not miss the deadline.

이 약은 식사 후에 먹으면 안 돼요.

• Natural: You must not take this medicine after meals.

💬 Advice & Warnings

그 사람한테 말하면 안 돼요. 비밀이에요.

• Natural: You must not tell that person. It's a secret.

포기하면 안 돼요. 할 수 있어요!

• Natural: You must not give up. You can do it!

혼자 가면 안 돼요. 위험해요.

• Natural: You must not go alone. It's dangerous.

그렇게 생각하면 안 돼요.

• Natural: You shouldn't think that way.

🏥 Health & Safety

술을 마시면 안 돼요. 약을 먹고 있어요.

• Natural: You must not drink alcohol. I'm taking medicine.

무리하면 안 돼요. 아직 완전히 안 나았어요.

• Natural: You must not overdo it. You haven't fully recovered yet.

이것은 아이들이 먹으면 안 돼요.

• Natural: Children must not eat this.

The Complete Three-Way System

Now that you've learned all three, here's the full picture:

With these four patterns, you can handle almost any situation involving rules, permission, and obligation.

Past Tense: Shouldn't Have / Wasn't Allowed

Replace 돼요 with 됐어요 (or 됐었어요 for further past):

Softer Alternatives

~(으)면 안 돼요 can sound direct or firm. In some situations, softer alternatives feel more natural:

뛰면 안 돼요. (You must not run - rule) 뛰지 마세요. (Please don't run - polite request)

Both are correct - the choice depends on context and relationship.

Real Conversations Using ~(으)면 안 돼요

📍 Conversation 1: At a museum

관람객: 여기에서 사진 찍어도 돼요? (Visitor: Is it okay to take photos here?)

직원: 죄송합니다. 이 구역에서는 찍으면 안 돼요. 저쪽 구역은 괜찮아요. (Staff: I'm sorry. You must not take photos in this area. The area over there is fine.)

관람객: 아, 알겠어요. 전시물을 만져도 돼요? (Visitor: Oh, I see. Is it okay to touch the exhibits?)

직원: 아니요, 만지면 안 돼요. 눈으로만 봐 주세요. (Staff: No, you must not touch them. Please just look with your eyes.)

📍 Conversation 2: Parent to child

엄마: 오늘 숙제 다 했어? (Mom: Did you finish your homework today?)

아이: 아직요. 게임 조금만 하면 안 돼요? (Child: Not yet. Is it okay if I play games just a little?)

엄마: 안 돼요. 숙제 먼저 해야 해요. 숙제하기 전에 게임하면 안 돼요. (Mom: No. You have to do your homework first. You must not play games before doing your homework.)

아이: 알겠어요, 엄마. (Child: Okay, Mom.)

📍 Conversation 3: Friends making plans

A: 오늘 파티에 좀 늦게 가도 돼요? (Is it okay if I come to the party a little late today?)

B: 조금은 괜찮아요. 근데 너무 늦으면 안 돼요. 케이크 자르는 시간이 있어요. (A little is fine. But you must not be too late. There's a cake-cutting time.)

A: 몇 시에요? (What time is it?)

B: 여덟 시요. 그 전에는 와야 해요. (8 o'clock. You have to come before then.)

Common Mistakes to Avoid

❌ Mistake 1: Confusing ~(으)면 안 돼요 with ~지 않아도 돼요

This is the most important distinction:

가면 안 돼요. = You must NOT go. (prohibition) 가지 않아도 돼요. = You don't HAVE TO go. (no obligation)

These are opposite meanings. Using the wrong one can cause serious misunderstanding.

❌ Mistake 2: ㄹ irregular - ㄹ stays in ~(으)면

❌ 만드면 안 돼요 ✅ 만들면 안 돼요 (ㄹ stays — no ㄹ drop here)

❌ Mistake 3: Using for yourself when you mean "I shouldn't"

In English, "I shouldn't" is a personal reflection. In Korean, ~(으)면 안 돼요 can be used for yourself too:

이렇게 생각하면 안 돼요. (I shouldn't think this way.) 포기하면 안 돼요. (I must not give up.)

This is perfectly natural - don't limit it to telling others what to do.

Quick Practice

Translate using ~(으)면 안 돼요:

1. You must not smoke here.
2. You must not be late.
3. You must not touch this.
4. Children must not drink this.
5. You must not give up.

Answers:

1. 여기에서 담배를 피우면 안 돼요.
2. 늦으면 안 돼요.
3. 이것을 만지면 안 돼요.
4. 아이들이 이것을 마시면 안 돼요.
5. 포기하면 안 돼요.

Summary

~(으)면 안 돼요 is the final piece of the obligation-permission system in Korean. With ~아/어야 해요, ~아/어도 돼요, and ~(으)면 안 돼요 all in your toolkit, you can navigate rules, set expectations, give advice, and understand what's allowed - in almost any situation.