To offer an uninterruptible power supply unit which can estimate an appropriate charge time and besides can reduce the size of its power unit by reducing a mounting space in the power unit.

This uninterruptible power supply unit is equipped with a battery charge control circuit 9 which switches, while it suppresses a power supply by the receiption of a system OFF signal from a system at the destination of the power supply, the charge current of a battery 11 into a current of a smaller value than that of the charge current supplied to the battery 11 when it receives a system-on signal.