PURPOSE: To make a magnetron hard to be subject to the influence of an external magnetic field and/or a magnetic substance as well as to simplify assembling jobs, simultaneously with miniaturization and rigidness in structure, by letting a leakage of magnetic flux decrease to the smallest possible extent in a way of forming a permanent magnet into an inner magnetic type, while installing an opening part in a yoke and feeding an output from this yoke opening to the external load.

CONSTITUTION: Each of annular permanent magnets 22 and 23 composed of anisotropic ferrite is disposed at both sides in a tube shaft direction of each of magnetic poles 16 and 17 via each of shim plates 20 and 21. At an anode cylinder 13, an output part 24 is projectingly installed sideways in an orthogonal direction toward a tube shaft, and a waveguide is coupled to this output part 24 whereby supported by a yoke 27 and locked thereat. On the other hand, the frame-like yoke 27 composed of soft steel used for an adapter plate in common is set up so as to surround the anode cylinder 13, permanent magnets 22, 23 and the waveguide all. An oscillated microwave output is led into the waveguide via the output part 24 and further fed to an external load circuit from an opening part 31 installed in the yoke 27.