A wireless power transfer system comprising: a power transmission unit that has a first resonance circuit including a power transmission coil ; a power reception unit that has a second resonance circuit including a power reception coil and a limiter, and wirelessly receives power from the power transmission unit ; and a controller that is configured to control power supply from the power transmission unit to the power reception unit , wherein the controller is configured to detect a change in a characteristic value related to the power supply, the change occurring depending on a misalignment amount between the power transmission coil and the power reception coil , characterised in that the controller is configured to perform a determination control operation of determining whether a misalignment between the power transmission coil and the power reception coil corresponds to a permissible range based on the change in the characteristic value, and wherein the controller is configured to determine that the misalignment corresponds to the permissible range when the characteristic value becomes equal to a threshold value smaller than a maximum value while the characteristic value decreases after the characteristic value becomes the maximum value from a lower value than a range of a value allowed to be taken by the characteristic value when the misalignment corresponds to the permissible range after the determination control operation starts, wherein the characteristic value is a voltage applied to the power reception unit by the power supply from the power transmission unit , wherein the limiter is configured to suppress the voltage (V 2 ) applied to the power reception unit at a suppression voltage (V L ) or less, and wherein the threshold value is set to the suppression voltage (V L ). a power transmission unit that has a first resonance circuit including a power transmission coil ; a power reception unit that has a second resonance circuit including a power reception coil and a limiter, and wirelessly receives power from the power transmission unit ; and a controller that is configured to control power supply from the power transmission unit to the power reception unit , wherein the controller is configured to detect a change in a characteristic value related to the power supply, the change occurring depending on a misalignment amount between the power transmission coil and the power reception coil , characterised in that the controller is configured to perform a determination control operation of determining whether a misalignment between the power transmission coil and the power reception coil corresponds to a permissible range based on the change in the characteristic value, and wherein the controller is configured to determine that the misalignment corresponds to the permissible range when the characteristic value becomes equal to a threshold value smaller than a maximum value while the characteristic value decreases after the characteristic value becomes the maximum value from a lower value than a range of a value allowed to be taken by the characteristic value when the misalignment corresponds to the permissible range after the determination control operation starts, wherein the characteristic value is a voltage applied to the power reception unit by the power supply from the power transmission unit , wherein the limiter is configured to suppress the voltage (V 2 ) applied to the power reception unit at a suppression voltage (V L ) or less, and wherein the threshold value is set to the suppression voltage (V L ). <EOS>