An electric power relaying unit of an image forming apparatus which includes an electric power blocking unit which selectively blocks the alternating current electric power output from the electric power input unit to be input to the electric power output unit, the electric power blocking unit including: a switching unit which switches an input of the alternating current electric power with respect to the electric power output unit; an electric power detecting unit which detects an electric power property; a memory unit in which a predetermined electric power property information is stored; and a control unit which controls a switching operation of the switching unit if determining that the detected electric power property corresponds to a predetermined electric power property in a failure of the image forming apparatus main body from a comparison result.