To prolong the service life of a battery without impairing a user's convenience.

A main controller 4 counts an operating time whenever an electronic apparatus 10 is used by the user, records the counted operating time to an operating-time recorder 41, and calculates a charging initiation level L and a charging termination level H based on the record of the operating time recorded in the operating-time recorder 41 (steps S17, S18). A charging controller 3 starts charging a secondary battery 1 by a charging circuit 2 when the present charging level of the secondary battery 1 is lower than the charging initiation level L, and stops charging the secondary battery 1 by the charging circuit 2 when the present charging level of the secondary battery 1 is higher than the charging termination level H.