PURPOSE: To smoothly grind a three-dimensionally curved surface by suspendingly providing a bracket having a driven pulley, being downwardly energized by means of a spring and putting a grinding belt around said driven pulley and a driving pulley, in a grinding device for a three-dimensionally curved surface.

CONSTITUTION: A large bevel gear 6 is fixed to a base plate 1, a main driving shaft 7 is loosely fitted in this gear 6, and a pair of side plates 9 are suspended from the lower parts 7a of the main driving shaft 7 in the vicinity of the large bevel gear 6. A driving shaft 12 having a driving pulley 17 is horizontally installed on the base parts 9a of the both side plates 9, and small bevel gears 13a, 13b are installed on the both end parts of the driving shaft 12 being meshed with the large bevel gear 6. A bracket 23 having a driven pulley 26 is suspendingly provided under the both side plates 9 while being downwardly energized by a spring 25, and a grinding belt 18 which is put around the driven pulley 26 and the driving pulley 17, rotates around its own axis while being turned around, to smoothly grind the three-dimensionally curved surface of a workpiece. Thereby, the whole unit can be miniaturized.