PURPOSE: To make it possible to decide the level of concentricity of an anode vane and a filament cathode of a magnetron, by applying a specific anode voltage to the completed magnetron, detecting the cathode current at the time, and deciding an adequate condition when the current level is more than a specific value.

CONSTITUTION: The relay 24 of an anode voltage converting unit 22 is kept to obtain a voltage to be 100% of a specific rating anode voltage, and examination items of various properties are measured. Then, the primary coil of an anode voltage transformer is converted to an intermediate tap 23a side furnished at a voltage divide transformer 23 by the relay 24, to make the anode voltage at about 80%. A current level deciding unit 30 is set to show the abnormal condition of the anode current Ib at the condition the anode voltage is converted to 80%. The signal at the time is delivered to a condition display unit 31, and the unit 30 records or reports the condition to the magnetron itself. After corresponding and comparing the allowable level of concentricity between the anode vane and the cathode, and the current level beforehand, the standard anode current level of deciding the adequate condition can be preset depending on the comparison, in the same type of magnetrons.