Power supply apparatus capable of detecting abnormality of current flowing through drive circuit

A current detection unit (60a) starts sampling of a motor current (MCRT) at the timing when the motor current (MCRT) has exceeded a threshold value (MCRT_std), and holds a maximum motor current value (MCRT_max) for each prescribed operation cycle. An abnormality determination unit (62a) determines whether the maximum motor current value (MCRT_max) is greater than the threshold value (MCRT_std), and counts the number of times that the maximum motor current value (MCRT_max) continuously exceeds the threshold value (MCRT_std). When the count value has reached at least 3, the abnormality determination unit (62a) generates and outputs a detection signal (DET) indicating abnormality in the motor current to a relay drive unit (64) and a notification unit (66). The relay drive unit (64) in receipt of the detection signal (DET) generates a signal (SE) to turn off the system relays. The notification unit (66) generates and outputs a signal AL to display means outside the power supply apparatus.