PURPOSE: To obtain a stable backup function as compared with the use of a button battery by connecting a charging capacitor and using a long-life solar battery to back up a memory.

CONSTITUTION: When a power supply of a camera is applied to a power supply terminal 1a, about 5V voltage is applied to a memory circuit 5 to actuate the circuit 5. At that time, the charging capacitor 9 of large capacity is charged with electric energy. Although about 3V voltage is generated by the solar battery 10 built in a camera body including an electronic view finder at that time, the voltage of the battery 10 is not used because about 5V voltage is applied in the positive direction of a diode 7. When the power supply of the camera is turned off, the capacitor 9 starts to discharge to the circuit 5 and the battery 10 charges the capacitor 9 to supply a backup voltage to the circuit 5 and back up the memory function.