In a non-contact electric power feed system, electric power is supplied in a non-contact manner from an electric power transmission device to a vehicle representing an electric power reception device. The electric power transmission device includes an electric power transmission unit, a communication unit for radio communication with the electric power reception device, and a control device for controlling the electric power transmission unit. The control device varies transmitted electric power from the electric power transmission unit while the electric power transmission unit transmits electric power, and determines whether or not pairing between the vehicle specified as an electric power transmission target and the electric power transmission unit is appropriate, based on information on variation in electric power from the vehicle specified as the electric power transmission target through radio communication.