A microwave oven comprising: a cabinet forming the exterior of the microwave oven; a base plate coupled to the cabinet and forming a bottom surface of the microwave oven; a rear plate coupled to the cabinet and forming a rear surface of the microwave oven; a cavity installed on the base plate so as to be spaced from the rear plate, thereby forming a space at a rear side of the base plate; a first high-voltage transformer positioned in the space, and installed in one side of the base plate; a second high-voltage transformer positioned in the space, and installed in the center of the base plate; a first magnetron positioned in the space and disposed in the opposite side of the first high-voltage transformer; a second magnetron positioned in the space and disposed over the first magnetron; a fan assembly positioned in the space and disposed over the first transformer; a fan housing covering the fan assembly and having an air introduction portion formed to face the first high-voltage transformer; and an air guide tube connected to the fan housing, and guiding an air flow generated by operation of the fan assembly to the first and second magnetrons (60,61), wherein the air guide tube is positioned in the space and has one side connected to the fan housing and the other side divided into two portions, a first divided portion is bent downward toward the first magnetron, and a second divided portion is bent upward toward the second magnetron, wherein the rear plate has a first discharge hole through which air having cooled down the first magnetron is discharged, and a second discharge hole through which air having cooled down the second magnetron is discharged, wherein the first discharge hole is formed at a place corresponding to the installation position of the first magnetron, and the second discharge hole is formed at a place corresponding to the installation position of the second magnetron, and wherein the air having cooled down the first magnetron is guided by a first connection tube and discharged to the outside through the first discharge hole, and the air having cooled down the second magnetron is guided by a second connection tube and discharged to the outside through the second discharge hole. a cabinet forming the exterior of the microwave oven; a base plate coupled to the cabinet and forming a bottom surface of the microwave oven; a rear plate coupled to the cabinet and forming a rear surface of the microwave oven; a cavity installed on the base plate so as to be spaced from the rear plate, thereby forming a space at a rear side of the base plate; a first high-voltage transformer positioned in the space, and installed in one side of the base plate; a second high-voltage transformer positioned in the space, and installed in the center of the base plate; a first magnetron positioned in the space and disposed in the opposite side of the first high-voltage transformer; a second magnetron positioned in the space and disposed over the first magnetron; a fan assembly positioned in the space and disposed over the first transformer; a fan housing covering the fan assembly and having an air introduction portion formed to face the first high-voltage transformer; and an air guide tube connected to the fan housing, and guiding an air flow generated by operation of the fan assembly to the first and second magnetrons (60,61), wherein the air guide tube is positioned in the space and has one side connected to the fan housing and the other side divided into two portions, a first divided portion is bent downward toward the first magnetron, and a second divided portion is bent upward toward the second magnetron, wherein the rear plate has a first discharge hole through which air having cooled down the first magnetron is discharged, and a second discharge hole through which air having cooled down the second magnetron is discharged, wherein the first discharge hole is formed at a place corresponding to the installation position of the first magnetron, and the second discharge hole is formed at a place corresponding to the installation position of the second magnetron, and wherein the air having cooled down the first magnetron is guided by a first connection tube and discharged to the outside through the first discharge hole, and the air having cooled down the second magnetron is guided by a second connection tube and discharged to the outside through the second discharge hole.