PURPOSE: To eliminate a human mistake at the times of the mounting of a photosensitive medium and the mounting of a magazines.

CONSTITUTION: In an image forming apparatus having a means 1 holding a recording medium 6 and a means holding a magazine receiving the recording medium 6 after recording, a discrimination device 19 discriminating the held recording medium 6 is provided and function changing the exposure quantity due to a laser irradiation device 17 on the basis of the discrimination result is provided. A provided and a means changing the exposure start time due to the laser irradiation device 17 on the basis of the discrimination result is provided and a comparison means comparing the discrimination result of the recording medium 6 due to the discrimination device is provided. By this constitution, the setting accompanied by printing can be automated.