A magnetron device, wherein a shield box is disposed on that side of a magnetron tube which faces a cathode stem; the shield box contains a choking system for preventing the leakage of microwave energy; and the choking system is formed of a pair of choking members, each of which has first and second choking elements, the first choking element being composed of a coil connected to a filament lead conductor and a high frequency core of high intrinsic resistivity received in the coil, and the second choking element being composed of a coil connected to the coil of the first choking element and a low frequency core of low intrinsic resistivity received in the second choking element coil.