PURPOSE: To better and transmission of heat from magnetron body to radiating fins as well as simplify the manufacture of the magnetron body by casting the magnetron body in the radiating fins.

CONSTITUTION: The radiating fins 8 and the cylindrical outer case 9 are formed by the casting of an aluminum elemental material. The cast molding 12 consists of the radiating fins 8 and the cylindrical outer case 9 obtained by setting the magnetron body 1 directly in a cast molder and then by casting a molten metal into the outside of the magnetron body 1 in such a way as to cast the magnetron body 1 into the cast molding 12. Furthermore, in the cast molding 12, the ring-like concave groove 8a' is formed in the inside of the inner cylinder 8a and the groove 8a' is coupled with the magnetic end plate 3 to prevent the loosing of the cast molding 12. The radiating fins 8 are cooled by supplying air through the vent 13 of the shield case 7.