PURPOSE: To continue an exposure work after release of an abnormality, by storing the amount of exposure existing before the extinguishment of a lamp due to the occurrence of the abnormality.

CONSTITUTION: When an exposure start signal is inputted to a port C, a transistor TR 5c is made conductive by the output from a port A, and a solenoid 4a is operated to operate a switch 4, and a lamp 1 is lit. The lighting time of the lamp 1 is counted in a CPU 5a. If an abnormality occurs to input an abnormality signal to a port B, the output of the port A is inverted, and the switch 4 is opened to extinguish the lamp 1. After the abnormal signal is released, the lamp 1 is lit again, and printing is continued on a basis of the stored exposure time.