べきではない

べきではない is the negative form of ～べき and expresses that someone should not or ought not to do something. It conveys a sense of moral obligation, social expectation, or strong principle – stronger than simply giving casual advice with 〜～ないほうがいい.

It is formed by attaching べきではない to the dictionary form of a verb:

べき vs. ほうがいい

While 〜～ないほうがいい is used for practical, everyday advice (e.g. "you shouldn't eat too much"), べきではない carries a stronger tone of moral judgment or principle. It suggests that doing the action would be wrong or inappropriate, not merely inconvenient.

する → すべき / するべき

The verb する has two accepted forms: すべきではない and するべきではない. The form すべき is slightly more formal and literary.

Polite form

In polite speech, ではない becomes ではありません. The more casual contraction じゃない is also common in spoken Japanese.

Usage notes

べきではない is used when talking about general principles, ethics, rules, or responsibilities. It can sound preachy or authoritative if used too directly toward someone, so it is used in impersonal statements or when expressing one's own beliefs about what is right or wrong.