PURPOSE: To limit the detection signal of a load current iL in the overload of the load current, to perform the current limitation of an active filter and to protect an apparatus from the overload in the active filter which compensates the harmonic current of a load.

CONSTITUTION: The current limitation method of an active filter is constituted of a control circuit 6 which is featured by that a limiter means 61 which limits a detection signal to a definite value or lower is installed on the output side of a load current detector 4 and that the output of the active filter 5 is limited in the overload of a rectifier load 2.