An antenna part of a magnetron includes an exhaust portion that is connected to an antenna conductor derived from an anode part and has an output terminal from which a microwave is outputted, and an output-side ceramic stem that holds internally the antenna conductor and is firmly fixed to the exhaust portion to insulate electrically a side pipe connected to the anode part of a main body of the magnetron from the exhaust portion. An antenna part further includes an antenna cap that is joined to the exhaust portion by a conductive adhesive arranged on an outer periphery of the exhaust portion. Accordingly, it is possible to provide the magnetron that can prevent occurrence of electric discharge between the antenna cap and the exhaust portion.