PURPOSE: To improve cooling characteristics and save materials by doubly bending the engagement section of cooling radiator fins provided on the external surface of a magnetron main body.

CONSTITUTION: A magnetron main body 1 consists of a cylindrical anode 1a with a number of vanes that are radially arranged inside, cathode input section 1b, and output section 1c and a number of aluminum cooling radiator fins 3 that radiate generated heat are provided on the external surface of the anode 1a. Besides, for the fins 3, the burring section 3a of a ring-shaped penetration hole is formed into a double bending structure and the inside diameter side of the burring section 3a is fit in the external surface of the anode 1a and then a folding piece 3b is stretched in the tube diameter direction. As a result, thermal conductivity can sharply be increased and cooling characteristics can be improved. Further, the engagement force into the anode 1a can be increased and the strength can be improved.