How to say "simple-minded" in Japanese

• 無邪気むじゃきJLPT N1approx.Common
  na-adjective, nounCovers 'simple-minded' in the innocent, artless sense: free of guile or malice, often endearingly naive. Typical of a child's trusting questions or an adult who takes people at face value without suspicion.
  彼女かのじょは無邪気むじゃきを装よそおった。↗

  She put on an air of innocence.
• 単純たんじゅんJLPT N3approx.Common
  na-adjective, nounCovers 'simple-minded' as uncomplicated thinking rather than innocence: it describes how a person's mind works in simple, straightforward ways. It can sound mildly critical, as when someone takes a problem too simply.
  彼かれの話はなしは単純たんじゅんそのものだった。↗

  His story was simplicity itself.

Choose 無邪気 for the innocent, artless side of 'simple-minded', an endearing lack of guile, and 単純 for a mind that is simple or uncomplicated, which can sound critical.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 無邪気むじゃきinnocent
• 単純たんじゅんsimple
• 甘っちょろいあまっちょろいoverly optimistic
• 単細胞たんさいぼうsimple-minded
• ちょろいsimple (way of thinking, etc.)