PURPOSE: To handle the battery without any anxiety in a state that the memory card is not installed in a terminal equipment, etc. by using plural pieces of batteries for backing up a volatile memory.

CONSTITUTION: In the case the memory card is not installed in a terminal equipment, a first battery 5 in the memory card backs up a volatile memory 2. When a first battery voltage drops to a first reference voltage or below, a second switch element 34 is turned on by an output of a first comparator 24 and a first display part 32 executes a display operation. When a first battery voltage drops to a second reference voltage or below, a third switch element 35 is turned on by an output of a second comparator 25 and a second display part 33 executes a display operation, and also, a first switch element 38 is turned on, and a second battery 21 backs up the volatile memory 2. In such a way, the battery can be handled without installing the memory card in the terminal equipment.