To provide a high frequency flaw detection method by which welding defects can be inspected in the online of the manufacture line of weldments and cost is reduced.

The high frequency flaw detection method detects the welding defect of a weldment 1 welded by using a high frequency current. The oscillation frequency of the high frequency current during welding is measured a plurality of times to obtain the change of two adjacent oscillation frequencies among the plurality of measured oscillation frequencies to detect the welding defects on the basis of this change. The varying waveforms of the plurality of measured oscillation frequencies are obtained to detect the welding defects on the basis of this varying waveform.