The present invention aims to provide a therapeutic or prophylactic agent for schizophrenia, which therapeutic or prophylactic agent can treat especially positive symptoms of schizophrenia and does not cause impaired information processing related to cognitive deficiencies or the like which is a symptom of schizophrenia. That is, a therapeutic or prophylactic agent for schizophrenia, comprising as an effective ingredient a compound having a specific morphinan skeleton represented by the compound 1 below or a pharmaceutically acceptable acid addition salt thereof, was provided.
