To provide an AC-DC converter that is highly efficient in a broad load current range from a light load to a heavy load.An AC-DC converter 1 has a main circuit and a control means 4; the main circuit includes a diode bridge circuit 3, a main inductor L1, a main switching element S1, a main diode D1, an auxiliary inductor L2, an auxiliary switching element S2, an auxiliary diode D2, and a smoothing capacitor C1 connected to a DC load 12. The AC-DC converter 1 supplies electric power from an AC power supply 11 to the DC load 12. In a period during which the instantaneous value of an input current from the AC power supply 11 is smaller than a prescribed value Ith, the AC-DC converter 1 stops the main switching element S1 and performs electricity conversion in hard switching by the operation of the auxiliary switching element S2.