To provide a novel rectifying device which suppresses the occurrence of a harmonic wave current.

The rectifying device includes, on its primary side, a sine wave oscillator 1 which oscillates a high frequency sine wave signal, and an amplifier circuit 2 for amplifying the output signal of this sine wave oscillator, which are connected in series with the primary winding of an isolation transformer transferring amplified sine wave signal to the secondary side. A rectifying circuit having rectifying elements D1, D2 and LC filter L2, C2 is connected to the secondary winding of an insulating transformer T. A capacitor C1 is connected in parallel with the secondary winding. The resonance frequency of an LC filter having this capacitor C1 and the leakage inductance L1 of the insulating transformer T is set to the arbitrary frequency by regulating the value of the capacitor C1.