A charge controlling circuit controls charging of a lithium-ion rechargeable battery. An electric power supplied from an external charger to the lithium-ion rechargeable battery is taken by a charging terminal. When the charging terminal is connected to the external charger, whether or not a charge prohibition condition is satisfied is determined by a CPU. A charging operation is prohibited when the charge prohibition condition is satisfied, but is permitted when the charge prohibition condition is not satisfied. Here, the charge prohibition condition includes a shortest time condition that a time during which the charging terminal is detached from the external charger is above a defined time decided in view of an instantaneous power interruption.