Abstract: A tool holding mechanism used in a bonder including a vertically moving member, a Y-direction oscillating plate installed on the vertically moving member so that the plate is rotated and then tightly secured to the vertically moving member, an X-direction oscillating plate installed on the Y-direction oscillating plate so that the X-direction oscillating plate is rotated in a direction perpendicular to the rotational direction of the Y-direction oscillating plate and then secured to the Y-direction oscillating plate, a Y-direction adjuster which rotates the Y-direction oscillating plate, an X-direction adjuster which rotates the X-direction oscillating plate, a tool attachment fixed to the X-direction oscillating plate, a .theta.-direction adjustment holder rotatably supported by the tool attachment block, a bonding tool being attached to this holder, and an .theta.-direction adjuster which is installed on the tool attachment block and finely rotates the .theta.