Schizophrenia is a disease whose symptoms are shown to a little less than 1% at adolescence. Since the morbidity elucidation is not yet made many of psychiatry diseases including schizophrenia, a useful biological marker or image inspection, and a physiological inspection are not in diagnosis. About diagnosis of a psychiatric disorder, the symptoms study diagnostic method never must be used. Then, diagnosis needs to be made appropriately and carefully and differential diagnosis must also perform it exactly. It is because medical treatment may differ depending on diagnosis. If this is not made appropriately, it may lead to medication of an unnecessary and aimless antipsychotic. In this paper, diagnosis and differential diagnosis of schizophrenia, and clinical course were summarized.