To provide a method for regulating an irreversible circuit element, in which demagnetization work is simple and change with time in magnetic force of a magnet is suppressed.

In the method for regulating a non-reciprocal circuit element, a non-reciprocal circuit element K comprising a ferrite member 5, a plurality of central conductors 6, 7 and 8 arranged on the ferrite member 5 to intersect partially, and a magnetic body 14 arranged to hold the central conductors 6, 7 and 8 between the ferrite member 5 and the magnetic body 14 and imparting a magnetic field to the central conductors 6, 7 and 8 is provided. After the magnetic body 14 has been saturation magnetized, to form a magnetically saturated magnet 2, the magnet 2 is demagnetized gradually from magnetically saturated state by one or a plurality of times of processing. Since the magnet 2 is to be only demagnetized, its regulation work is facilitated, and changes due to aging in the magnetic force of the magnet 2 is suppressed.