PURPOSE: To obtain photographic characteristics of the laser photosensitive material which are correlative to those when an actual laser image setter by using a laser as a light source for scanning exposure.

CONSTITUTION: The laser beam emitted from the laser diode light source is collimated by a collimator lens 2 into parallel luminous flux, which is made incident on a polygon mirror 3 and deflected. The deflected laser beam is converged by an f.θ lens 4 on a sample surface 6 is exposed by scanning corresponding to the deflection. Further, the drum which holds the sample rotates corresponding to the deflection period until the exposure is completed. At this time, the energy of the laser beam irradiating the sample is varied by a gray optical wedge 5 and after the exposure, the sample is developed to obtain the photographic characteristics of the red sensitive silver salt photosensitive material from a characteristic curve. Consequently, the photographic characteristics of the laser photosensitive material which are correlative to those when the actual laser image setter is used are obtained.