To obtain a method and an apparatus for restarting the motor of a submerged pump which receives liquid pressure after power interruption.

The restarting method for the motor 104 of a submerged pump 106 is as follows: The time when power to a restarting apparatus is restored is detected first, and a control device 120 samples signals sent back from the motor to which power is not supplied to determine the frequency and phase sequence of the signals. Based on the determined frequency and phase sequence, the speed and direction of the operation of the motor are determined, and the first pulse width modulation waveform fit to the determined speed and direction of the motor is supplied to the motor. The output frequency of the waveform is adjusted so that the speed and direction of the operation of the motor are adjusted until the motor reaches desired speed and direction of operation.