There is provided a power supply unit, comprising: a converter transformer; a first low voltage generation unit to generate a first voltage on a secondary side of the converter transformer and output the first voltage; a first controller that controls an activation state of a primary side of the converter transformer based on the first voltage; an inactivation unit to inactivate operation of the first controller based on the first voltage to let the first low voltage generation unit to suspend output of the first voltage; a high voltage supply unit to output a high voltage higher than the first voltage by using the first voltage; a detection unit to detect an anomalous state concerning output of the high voltage of the high voltage supply unit. The high voltage supply unit inactivates the operation of the first controller through the inactivation unit when the anomalous state is detected.