Tree drawing tests, in which patients draw a picture of a tree with nuts, have often been used in psychosomatic internal medicine as a conventional psychological test. The tests guess their character and mental state from the morphological feature of trees. Their picture was analyzed using an image processing method, and the characteristic quantities were calculated. We considered relationship between those indices and their mental conditions, such as their depression scale. As a result, the picture features allow psychiatrists to diagnose their psychiatric disorder and perform more effective diagnosis with patients.