A power transfer device includes a power transfer part configured to contactlessly transfer power to a power reception part of a power reception device, a sensor configured to detect a foreign object that is present between the power transfer part and the power reception part, and a controller configured to control the power transfer part and the sensor. The controller is configured to execute initial learning that learns an initial state of a detection result of the sensor before initiation of foreign object detection using the sensor. The controller is configured to determine presence of the foreign object by using a difference between the initial state and the detection result of the sensor after execution of the initial learning. The controller is configured to control the power transfer part to reduce power to be transferred to the power reception part when the initial learning is not normally executed.