A frame fixing jig for mounting on a chuck table has a chuck portion for holding a workpiece in an annular frame, and a body portion for supporting the chuck portion. A frame support member (FSM) supports the annular frame, and a ring presses the frame against the FSM. The FSM has a through hole. The ring has an annular base portion and an engaging portion. The engaging portion can be inserted through the through hole, thereby engaging the FSM. The engaging portion includes a rotating shaft extending through the annular base portion, a knob fixed to the upper end of the shaft, and a plate fixed to the lower end. The surface around the lower end of the through hole or the upper surface of the plate is formed with an inclined surface for lowering the rotating shaft by rotating the plate inserted through the through hole.