PURPOSE: To prevent the fluctuation of density of a recorded image caused by the relative humidity change of an exposed part of a photosensitive material with use of an inexpensive means by setting the DC gain of an optical output stabilizing circuit at such a low level that can change the driving current-optical output characteristic of a semiconductor laser in response to the temperatures.

CONSTITUTION: An image signal generator 10 outputs an image signal S1 based on a picture element clock S3 to hold the continuous images. The signal S1 is converted into a light emitting level command signal S5 after undergoing the corrections like the correction of gradation, the antilogarithmic conversion, etc., through a correction table 11. Then the signal S5 is converted into a command signal Vref by a D/A converter 12 and inputted to an addition point 2 of an APC circuit 8 of the low sensitivity. A light beam 4 is generated to the signal Vref via the current/voltage converter amplifiers 3 and 7, a semiconductor laser 1, and a photodiode 6. The beam 4 scans a photosensitive material 20 via a collimator lens 17, a polarizer 18, and a condenser lens 19 for generation of a latent image. The material 20 is passed through a developing machine 22 for generation of the continuous images.