A workpiece holder comprises: a holding table including: a chuck mechanism holding the workpiece; a positioning mechanism moving the chuck mechanism in a direction orthogonal to the rotary axis while supporting the chuck mechanism to locate the workpiece; and a rotary mechanism rotating the positioning mechanism about the rotary axis to rotate the workpiece held by the chuck mechanism about the rotary axis; an alignment imaging part capturing an image of the outer peripheral portion of the workpiece held by the chuck mechanism; a misalignment detector detecting misalignment of the symmetry axis with respect to the rotary axis based on the captured image while the workpiece is rotated by the rotary mechanism; and a workpiece position correction part correcting the position of the workpiece to match the symmetry axis with the rotary axis by moving the chuck mechanism using the positioning mechanism to eliminate the misalignment.