Friction stir welding apparatus

A friction stir welding apparatus comprising a rotating tool including:

• an upper rotating body arranged to be adjustable in position in an axial direction by an actuator for upper rotating body;
• a lower rotating body formed integral with a rotating main rod extending through the upper rotating body and arranged to be adjustable in position in the axial direction by an actuator for lower rotating body;
• and a stirring part formed in the rotating main rod, the apparatus being configured such that the upper rotating body and the lower rotating body clamp therebetween a joint of members to be joined placed with their end faces butting each other and the stirring part is rotated to stir the joint by frictional heat to join the members,
• wherein the rotating tool includes a slide plate attached, through a thrust bearing, to one or both of end portions of the upper rotating body and the lower rotating body facing each other.