To obtain new power by obtaining output power larger than input power.

This power multiplier is characterized in that: a capacitor, an inductance and a load are connected to a secondary circuit of a power supply transformer in an AC electric circuit; and a large phase-advance current is made to flow by generating a resonance phenomenon by the effective inductance of a secondary coil of the transformer and the capacitor; thus making load power larger than input effective power. A power generating unit returns part of an output of the power amplifier to an input, and does not necessitates energy.