A cooking apparatus, comprising: - an external case; - a cooking cavity positioned within the external case; - an upper space located over the cooking cavity; - two lateral spaces located at two opposite lateral sides of the cooking cavity; - a lower space located below the cooking cavity; a first opening provided in the cooking cavity, the first opening is formed in one of the two opposite lateral sides thereof; a second opening formed in the other one of the two opposite lateral sides thereof; and characterized by a rear space located behind the cooking cavity, wherein an inlet is provided at the rear space and a component room is provided in the rear space; - a cooling flow path in which cooling air flows from the inlet at the rear space into the upper space and/or the lateral spaces, and consecutively to an outlet provided at the lower space; - a magnetron provided at the component room in the rear space and providing microwaves to the cooking cavity, - a flow guide located on the cooling flow path for connecting the magnetron provided in the rear space to the first opening formed in one of the two opposite lateral sides of the cooking cavity; - a first flow path that directs flow from the magnetron in the rear space into the cooking cavity through the first opening and directs out of the cooking cavity through the second opening; and - a second flow path that extends from the rear space so as to intersect with the first flow path as it directs flow out of the second opening, wherein the second flow path drives the flow to the outlet at the lower space and then to an outside of the cooking apparatus. - an external case; - a cooking cavity positioned within the external case; - an upper space located over the cooking cavity; - two lateral spaces located at two opposite lateral sides of the cooking cavity; - a lower space located below the cooking cavity; a first opening provided in the cooking cavity, the first opening is formed in one of the two opposite lateral sides thereof; a second opening formed in the other one of the two opposite lateral sides thereof; and characterized by a rear space located behind the cooking cavity, wherein an inlet is provided at the rear space and a component room is provided in the rear space; - a cooling flow path in which cooling air flows from the inlet at the rear space into the upper space and/or the lateral spaces, and consecutively to an outlet provided at the lower space; - a magnetron provided at the component room in the rear space and providing microwaves to the cooking cavity, - a flow guide located on the cooling flow path for connecting the magnetron provided in the rear space to the first opening formed in one of the two opposite lateral sides of the cooking cavity; - a first flow path that directs flow from the magnetron in the rear space into the cooking cavity through the first opening and directs out of the cooking cavity through the second opening; and - a second flow path that extends from the rear space so as to intersect with the first flow path as it directs flow out of the second opening, wherein the second flow path drives the flow to the outlet at the lower space and then to an outside of the cooking apparatus.