A magnetron includes inner and outer strap rings for providing a linkage among vanes which are disposed inside of an anode cylinder. The inner and outer strap rings have their diameters determined such that their algebraic mean is 1.75-1.95 times the diameter of an interaction space defined by the inner tips of the vanes. The magnetron structure achieves a significant leakage supression effect against spurious microwaves, particularly the fifth harmonic.
