To provide a means capable of accurately detecting the occurrence of tracking phenomena since a large number of recent electrical machinery and apparatus have a power source which does not use a transformer but directly rectifies a commercial alternating current and smoothes it by a capacitor and intentionally control a current waveform by frequency control and SCR firing angle control such as inverters and since current waveforms of those machinery and apparatus are not simple sine waves and currents due to the use of general machinery and apparatus are scarcely accurately distinguishable from currents due to tracking phenomena.

A tracking electric current detection apparatus includes the amount of change of high-order harmonic components of current as a determination factor of detection.