A coil unit, a wireless power feeding device, a wireless power receiving device, and a wireless power transmission device are provided that are capable of reducing high voltage induced on the metal part. A coil unit Lu1 includes a power transmission coil L1, a first reactance circuit X10 that is connected to one end portion of the winding of the power transmission coil L1 and forms a resonant circuit together with the power transmission coil L1, a metal part SD disposed on the same side as the back side of the power transmission coil L1, and a first adjustment capacitor C10 connected between the other end portion of the winding of the power transmission coil L1 and the metal part SD.