A vehicle power supply apparatus includes a motor generator, a first electricity storage device, a second electricity storage device, a switch, a switch controller, and an electricity storage device determiner. The switch controller is configured to cause the first cutoff state of the switch, switchable between a first electrically conductive state that allows the motor generator and the first electricity storage device to be coupled to each other and a first cutoff state that allows the motor generator and the first electricity storage device to be isolated from each other, to be maintained in a situation where the first electricity storage device discharges beyond a threshold, on a condition that the switch is switched to the first cutoff state in accordance with controlling of the motor generator into a powering state and the second electricity storage device is determined as being in an abnormal state.