A magnetron includes a yoke, an upper magnet, an upper pole piece located at a lower side of the upper magnet, a fifth-harmonic-frequency choke located at an upper side of the upper pole piece, a third-harmonic-frequency at a lower side of the fifth-harmonic-frequency choke, a ceramic part located at an upper end of the fifth-harmonic-frequency choke and configured to output an electromagnetic wave including a plurality of frequencies, a fourth-harmonic-frequency choke that is bent inward from the ceramic part and that is welded to an upper end of the ceramic part, and a second-harmonic-frequency choke that is welded to the fourth-harmonic-frequency choke and that extends upward and downward along a heightwise direction. The third-harmonic-frequency choke, fifth-harmonic-frequency choke, and second-harmonic-frequency choke are configured to block harmonic frequencies of the electromagnetic wave.