a cathode structure of a magnetron which is used for microwave ovens , industrial microwave heating , and medical purposes is disclosed . one of two leads of the cathode structure of the magnetron , that is , one of a center lead and a side lead is tightly fitted into the spacer , and a metal fixing material is poured into the fitting portion and is fixed thereto . a hole of the spacer for inserting the other of the two leads has looseness with respect to the other of the two leads . the friction between the other of the two leads and the spacer is reduced , and even when the leads are made thin , the strength of the cathode structure is not reduced , and the production of extraneous sounds can be suppressed .