A magnetron includes: an anode tube; and cooling fins placed on a periphery of the anode tube and arranged along a central axis of the anode tube. Each of the cooling fins includes at least two sets of fins formed by cutting a part of the cooling fin, and performing different bending works on the cut portions, respectively, so as to form a region where the cooling fins are dense and a region where the cooling fins are sparse, when viewed in a flowing direction of a cooling medium which cools the anode tube through the cooling fins. The at least two sets of fins are bent at bending angles such that intervals of the cooling fins in the region where the cooling fins are dense are ½ or less of placement intervals of the cooling fins.