A cooking apparatus comprising: a cavity unit having a cooking chamber therein, a side wall plate with a discharge hole section therein, and a rear wall plate having an introduction hole section (161, 162, 163, 164) therein; a door unit on the cavity unit, configured to open and close an opening of the cavity unit; a convection heater unit on the rear wall plate, configured to generate heat to be supplied to the cooking chamber through the introduction hole section (161, 162, 163, 164); a circulation duct unit connected to the discharge hole section, configured to guide air from the cooking chamber back to the cooking chamber; wherein the circulation duct unit comprises a circulation duct having one end connected to the discharge hole section and another end connected to a suction hole section of the side wall plate, configured to guide air to the suction hole section, characterized in that the cooking apparatus further comprises an introduction opening and closing unit configured to open and close the introduction hole section (161, 162, 163, 164) and control an amount of heat supplied to the cooking chamber, and in that the circulation duct unit further comprises a duct opening and closing section on the circulation duct, configured to open and close an internal flow path of the circulation duct, and the circulation duct comprises a discharge opening configured to discharge air from the discharge hole section to an outside of the circulation duct, and the duct opening and closing section closes the discharge opening when the internal flow path of the circulation duct is open, and opens the discharge opening when the internal flow path of the circulation duct is closed. a cavity unit having a cooking chamber therein, a side wall plate with a discharge hole section therein, and a rear wall plate having an introduction hole section (161, 162, 163, 164) therein; a door unit on the cavity unit, configured to open and close an opening of the cavity unit; a convection heater unit on the rear wall plate, configured to generate heat to be supplied to the cooking chamber through the introduction hole section (161, 162, 163, 164); a circulation duct unit connected to the discharge hole section, configured to guide air from the cooking chamber back to the cooking chamber; wherein the circulation duct unit comprises a circulation duct having one end connected to the discharge hole section and another end connected to a suction hole section of the side wall plate, configured to guide air to the suction hole section, characterized in that the cooking apparatus further comprises an introduction opening and closing unit configured to open and close the introduction hole section (161, 162, 163, 164) and control an amount of heat supplied to the cooking chamber, and in that the circulation duct unit further comprises a duct opening and closing section on the circulation duct, configured to open and close an internal flow path of the circulation duct, and the circulation duct comprises a discharge opening configured to discharge air from the discharge hole section to an outside of the circulation duct, and the duct opening and closing section closes the discharge opening when the internal flow path of the circulation duct is open, and opens the discharge opening when the internal flow path of the circulation duct is closed.