In this paper, diagnosis of depression was deliberatively considered from a view of psychopathological studies, and problems of operational diagnostic system in psychiatry were discussed. For good clinical practices, 1）diagnosis must be considered as a part of clinical practices. 2）diagnosis must be closely related to therapeutic works, 3）the process of making a diagnosis itself should be managed to be remedial, and 4）a clinical category is expected to contain not only a summation of individual cases, and at the same time the link between the category and individual cases should not be abandoned. The author also discussed about some clinical maneuvers.