PURPOSE: To copy originals at a prescribed density by a low exposure energy by beginning to charge a main capacitor for a flash lamp after a platen plate attains a 1st set temperature and making the flash lamp emit light when the platen plate reaches a 2nd set temperature and when the main capacitor is charged to a prescribed potential.

CONSTITUTION: When the platen plate is heated, a temperature control part monitors a signal from a temperature detection thermister provided close to the platen plate or provided by bringing into contact with said plate. When the platen plate attains the 1st prescribed temperature, 40°C, for instance, an operation control parts starts charging the main capacitor. When the platen plate attains the 2nd prescribed temperature, 45°C, for instance, a signal is again transmitted to the operation control part, and conduction to a heater stops. According to the signal that the thermister detects, the temperature control part continues or cut the conduction to the heater hence onward, whereby the temperature of the platen plate is kept within a given range, 45W50°C, for instance. When charging the main capacitor is completed, the operation control part outputs a display to show that the flash lamp can light up.