To provide a power supply unit of an image formation device which facilitates the power supply management of the device and enables the unit price of the applied switches to be reduced.

The power supply unit includes a power supply part which makes an alternate current rectified and converted into a designated direct current that is applied as the operational power for at least one functional module forming the image formation device, a change part installed between the output end of the power supply part and the power input end of each functional module, and a power-saving switch which is installed in a control part turning-off the change part at the time of approaching the power management mode of the image formation device and, at turning-off, applies the output voltage of the power supply part to the control part to apply the applied output voltage as a signal for setting the power management mode.