A cooling apparatus of a cooking appliance including a cabinet having a cooking chamber located therein and an electric component chamber located outside the cooking chamber; a door installed on the cabinet for opening and closing the cooking chamber, and having a suction channel and a discharge channel communicating with the electric component chamber; and an air blower installed in the electric component chamber for sucking air to the inside of the electric component chamber through the suction channel and the discharge channel of the door and discharging the air, so that the external air having a low temperature is directly sucked through the door, cools the electric component chamber, and is then discharged to the outside, thereby increasing cooling efficiency of the door.