To let a user accurately recognize the recharging period of a battery by calculating the consumption of the battery per specific time, and calculating a value regarding the remaining capacity of the battery from the calculated consumption and notifying it.

The battery remaining capacity ratio and the remaining battery usable time are calculated from battery mean consumption related to an inputted user name in a battery consumption data base stored on a hard disk 204 and the battery remaining capacity of the dedicated battery 219 which is monitored. The battery remaining capacity ratio and the remaining battery usable time which are calculated are displayed on an LCD 209 to make the user recognize the recharging period. Namely, the battery consumption per specific time is calculated according to changes in use state to make the user accurately recognize the recharging period of the battery. Consequently, the user's handleability can be improved.