An image forming apparatus detects whether a cover is opened or closed in each of a general power mode and a power saving mode. The image forming apparatus includes a cover opening/closing sensor to detect opening or closing of a cover, a cover opening/closing sensing power-supply input unit to provide or not to provide a voltage different from an operation voltage of the image forming apparatus, to the cover opening/closing sensor according to the opening or closing of the cover, and an interlock switch to connect or not to connect the cover opening/closing sensor to the cover opening/closing sensing power-supply unit according to the opening or closing of the cover.