A power transfer device comprising: 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, wherein: 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; and 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, the power transfer device being characterized in that it further comprises an input part configured to receive an instruction to execute the initial learning from a user, wherein the controller executes the initial learning when the input part receives the instruction from the user, and the initial state is a state of the detection result of the sensor in a state where a foreign object is not present between the power transfer unit and the power reception unit. 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, wherein: 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; and 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, the power transfer device being characterized in that it further comprises an input part configured to receive an instruction to execute the initial learning from a user, wherein the controller executes the initial learning when the input part receives the instruction from the user, and the initial state is a state of the detection result of the sensor in a state where a foreign object is not present between the power transfer unit and the power reception unit. 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; and 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, the power transfer device being characterized in that it further comprises an input part configured to receive an instruction to execute the initial learning from a user, wherein the controller executes the initial learning when the input part receives the instruction from the user, and the initial state is a state of the detection result of the sensor in a state where a foreign object is not present between the power transfer unit and the power reception unit.