A non-contact power supply device comprising: a non-contact power supply circuit supplying AC power in a non-contact manner with the circuit being configured by a power supply element disposed in a power supply section and a power receiving element disposed in a power receiving section capable of being relatively displaced with respect to the power supply section facing each other; a phase difference detecting section detecting a phase difference (θ) between a voltage phase (θ V) of an AC voltage (Va) applied to the non-contact power supply circuit in the power supply section and a current phase (θ I) of an AC current (Ia) flowing through the power supply element, the phase difference (θ) changing depending on a relative positional relationship between the power supply element and the power receiving element; and a determination section determining the relative positional relationship between the power supply element and the power receiving element based on the phase difference (θ) characterized in that: the determination section determines whether or not the power supply element and the power receiving element face each other based on a result of comparison between the phase difference (θ) and a predetermined phase threshold (Φ), wherein the determination section performs control such that the AC voltage (Va) is at a high level when it is determined that the power supply element and the power receiving element face each other, and wherein the determination section performs control such that the AC voltage (Va) is at a low level within a range in which the phase difference (θ) can be detected by the phase difference detecting section when it is determined that the power supply element and the power receiving element do not face each other. a non-contact power supply circuit supplying AC power in a non-contact manner with the circuit being configured by a power supply element disposed in a power supply section and a power receiving element disposed in a power receiving section capable of being relatively displaced with respect to the power supply section facing each other; a phase difference detecting section detecting a phase difference (θ) between a voltage phase (θ V) of an AC voltage (Va) applied to the non-contact power supply circuit in the power supply section and a current phase (θ I) of an AC current (Ia) flowing through the power supply element, the phase difference (θ) changing depending on a relative positional relationship between the power supply element and the power receiving element; and a determination section determining the relative positional relationship between the power supply element and the power receiving element based on the phase difference (θ) the determination section determines whether or not the power supply element and the power receiving element face each other based on a result of comparison between the phase difference (θ) and a predetermined phase threshold (Φ), wherein the determination section performs control such that the AC voltage (Va) is at a high level when it is determined that the power supply element and the power receiving element face each other, and wherein the determination section performs control such that the AC voltage (Va) is at a low level within a range in which the phase difference (θ) can be detected by the phase difference detecting section when it is determined that the power supply element and the power receiving element do not face each other.