It is not long since clinical psychology became a popular subject of study in Japan. Therefore, studies on the method of diagnosing and treating the patients have not been sufficiently made. The writer of this article wants to comment on methodology of clinical psychology. 1. Needless to say, clinical psychology aims to treat and cure the patients. Its practice calls for specific techniques as well as careful examination of general (or theoretical) psychology. 2.“To diagnose” means to detect the cause of the illness for treatment. To give correct diagnosis, clinicians should be versed with Jaspers' theory of method. Jaspers contends that it is most important in psychopathological studies to apply understanding (verstehende) psychology and explaining (erklaerende) psychology independently. 3. There are three methods in psychotherapy: namely, directive, non-directive and psychoanalytic. Only in actual practice, should one decide which of the three methods is desirable.