PURPOSE: To prevent data recorded on an amorphous semiconductor thin film from being erased by laser light by providing a photo shutter, showing electro-photo effect, on a light path between a light emitting unit and the thin film.

CONSTITUTION: On laser light path 12 between light emitting unit 1 and magmifying lens 2, shutter 2, of liquid crystal, etc., displaying electro-photo effect is provided. Photo shutter 22 is connected to photo-shutter controller 22. The controller 22, retrieval command signal (a) and end signal (b) from the controller are inputted to control shutter 21, allowing laser light to pass during the rise of signal (a) and the fall of (b). Therefore, amorphous semiconductor thin film 5 is never irradiated with reproducing laser light for a long time, so that data recorded on thin film 5 will not be erased by the laser light.