To provide a method for saving power which can be easily applied at the same linkage connection point as in the DC linkage, whether a load is already established or newly established, without the need for modifying the load side and which makes the back power flow possible and also provide a power saving linkage equipment using this method.

Commercial AC power is stepped up and rectified, by means of a rectification-side switching circuit 7 constituting a bridge circuit together with a reactor 3 installed at the input side. This step-up point is applied with power by means of a power generating means separated from the commercial AC 17 and the stepped-up and rectified power is inverted by means of an inversion-side switching circuit constituting a bridge circuit installed at the output side, and then AC power is supplied to a load.