An image forming apparatus for controlling power supply is provided. An image forming apparatus includes at least one cover unit to be mounted in the image forming apparatus, at least one replaceable unit to participate in an image forming operation of the image forming apparatus, a sensing unit to sense whether the at least one cover unit is opened or closed, and a main board unit to cut off the power supply to the at least one replaceable unit for a predetermined period of time when the at least one cover unit is opened or closed. Accordingly, stable operation is enabled.