An image forming apparatus to safely supply or interrupt power according to opening or closing of a cover includes a power source unit to output low power and high power, an interlock switch unit to be turned on or off according to opening or closing of a cover, and an engine power circuit unit. The engine power circuit unit includes cover opening/closing sensing switches connected to the interlock switch unit to be turned on or off according to whether the interlock switch unit is on or off, and power supply switches connected to the power source unit to apply or interrupt the power from the power source unit according to a determination of whether the cover opening/closing sensing switches are on or off.