An oscillation jig includes: an oscillation jig base connected to an oscillation table; a first clamp member provided in the oscillation jig base; a second clamp member located at a position opposed to the first clamp member in an oscillation direction and configured to hold a first metal component together with the first clamp member; a link mechanism provided in the oscillation jig base, composed of a plurality of links connected together, connected to the second clamp member, and caused to extend and contract in the oscillation direction; and a clamp actuator configured to cause the link mechanism to extend and contract in the oscillation direction. When the first clamp member and the second clamp member hold the first metal component, a connection center line connecting connection centers of the respective links is made straight in the oscillation direction.