The present invention improves charging efficiency in a wireless power transfer device. A wireless power transfer device wirelessly transfers power by using inductive coupling to a charging target device placed in the vicinity of a charging pad. The wireless power transfer device includes an amplifier for performing power amplification, a series resonant circuit constituted by a resonant capacitor and a power transfer coil, and a foreign material detection unit for detecting a non-charging device, which is not a charging target, placed in the vicinity of the charging pad. The foreign material detection unit is constituted by a pick-up coil, bandpass filters, detector circuits and a control circuit. The foreign material detection unit detects an IC card which is the non-charging device by a signal component emitted through inductive coupling with the power transfer coil from the device placed in the vicinity of the charging pad when transferring power.