The invention discloses an image forming apparatus including: a main body; a cover rotatably connected to the main body; a power-supply unit to generate a first power-supply voltage and a second power-supply voltage; an image forming engine to receive the first power-supply voltage from the power-supply unit; a control unit to receive the second power-supply voltage from the power-supply unit, and to stop an operation of the image forming engine, when the second power-supply voltage is cutoff. The image forming apparatus further includes a power-supply cutoff unit that delays a cutoff time ofthe first power-supply voltage, as compared to a cutoff time of the second power-supply voltage, according to an opening of the cover. The cutoff unit includes a first switch to cutoff first power-supply voltage to the image forming engine, and a second switch to cutoff the second power-supply voltage to control unit. The first and second switches are sequentially switched off when the cover is opened. The first and second switches are arranged to cutoff the second power-supply voltage before the first power-supply voltage is cutoff.