PURPOSE: To prevent an alarm from being outputted by erroneously recognizing wrong wiring when a load connected to a current system is decreased and a power factor is led by the leading power factor capacitor of a base.

CONSTITUTION: This device is provided with a signal input means (changeover switch) 101 and an alarm lock circuit 10 for stopping outputting the alarm from an erroneous input judge alarm circuit 8 based on an input signal from this signal input means. At the time of checking wrong wiring to be performed when installing this power factor controller, the alarm is outputted and after the wrong wiring is checked, the output of the alarm is stopped.