A magnetron sputtering device is provided with: a target part positioned in such a manner as to face a substrate held by a substrate holding part; a power source that supplies power to the target part; a magnet part that moves back and forth along the rear of the target part; a chamber having side walls that are electrically grounded; and a power source control part that controls the power source in such a manner that, while the magnet part is away from approach points, which are points respectively closest to the side walls, a prescribed voltage is applied to the target part by the power source, but the prescribed voltage is reduced when the magnet part reaches one of the approach points.