To provide an image forming device in which the action of switching between a power saving mode and a normal mode does not occur frequently by setting a time zone when the performance of the power saving mode is prohibited on a user side and that effectively demonstrates a power saving effect.

The image forming device with a power saving function automatically shifts into a power saving mode when waiting for processing continues for a prescribed period. The device has a means to set a time zone when the performance of the power saving mode is prohibited, and a clock means. The device has a control means to retain a normal mode if the present time is within the time zone inhibiting the power saving mode.