To restrain the lowering of the image quality of a recorded image caused by the deviation of an image formation point position by saving manpower for testing the lowering of the image quality of the recorded image associated with the deviation of the image formation point position of an image formation optical system.

A test print original image is plurally exposed on a photographic printing paper while the position of an exposing lens is moved by specified amount. The plural test print images visualized through such processing as developing are respectively image-picked up, and edges are extracted from the respective test print images. Next, the average values of the differential (density change value) on the extracted edges are respectively arithmetically calculated as the definition featured values of the respective test print images, relation between the position of the exposing lens and the definition featured value of the test print image is found based on the position of the exposing lens obtained when the respective test print images are exposed and the definition featured values of the respective test print images, and the exposing lens is moved to an optimum position where the definition featured value is maximum.