PURPOSE: To determine a service life of a battery to be used according to final voltage depending on a type of the battery and effectively utilize the battery by detecting output voltage of the battery to be used at different time points and determining the type of the battery.

CONSTITUTION: A monitor device 40 comprises a liquid crystal display device 42 and a battery 44 as its power source, while a detecting circuit 56 detects an output voltage level of the battery 44. First, the voltage of the battery 44 is compared with a constant value which is irrespective of a type of the battery, and if the voltage is smaller than the value, the battery is replaced with a new one. If the voltage is higher, the battery voltage value is stored in a variable X0 and then stored in a variable X1 when a motor 24 is driven, and a difference between X0 and X1 is compared with a predetermined value. Thus the type of the battery is determined from a difference between times with different load, such as time with a shutter activated and time not activated, or with power supplied to a recording system and a reproducing system and without power supplied, and according to final voltage depending on the type of the battery, a service life of the battery is determined. Thus replacement, etc. of the battery can be indicated depending on the type of the battery, permitting the battery to be effectively utilized.