PURPOSE: To lessen clearance between radiator plates as well as reduce the deformation of the radiator plates by using a part of hold a magnetron body, a part to press the radiator plate into the body, and a part to deform the radiator plate pressed in a given direction.

CONSTITUTION: In the receiving base 12, the hole 13 in which the lower end portion of the body 11 is situated is provided without holding directly the body 11, and the inside circumference of the hole 13 is provided with the receiving part 35 to hole the body 11 in a vertically movable manner. The receiving part 35 has the tiered portion 36 at which the inside circumference of the part 35 is fitted on the lower shoulder of the body 11 for positioning. Also, the upside 37 of the receiving base 12 is so inclined that it is situated toward opposite to the press-in direction from the peripheral end of the radiator plate 18a placed on the upside 37. The inclined upside 37 serves as a part to deform the radiator plate 18a.