PURPOSE: To apply stable double head surface grinding work even in the case of a thin workpiece, by giving tensile force from a peripheral side to a carrier, and holding the workpiece to this carrier fed into between grinding wheels rotated at a high speed.

CONSTITUTION: A plurality of tension bolts, insertion screwed to circumferentially equally arranged position of a clamp ring 17, are tightened to give tensile force from a peripheral side to a carrier 13. Magnets 11, 12 are rotated at a high speed in a reverse direction to each other, also to rotate the carrier 13, for instance, by about 1 turn per minute by a carrier driving motor 21. In this condition, when a workpiece 14 is supplied to a holding hole 15 of the carrier 13 in a prescribed position by a supplier device, this workpiece 14 is fed into between the magnets 11, 12 left as held to the holding hole 15 of the carrier 13 to be rotated at a high speed according to rotating the carrier 13, here to perform double head surface grinding the workpiece by the magnets 11, 12.