To provide a thermal deformation prevention device which in simultaneous working of surface-rear surface of a thin disk-like workpiece, restrains thermal deformation of a static pressure pad for hydrostatically supporting both surface and rear surface of the workpiece.

The thermal deformation prevention device 6 restrains the thermal deformation of a pair of static pressure pads 15 and 16 for supporting both surface and rear surface Wa and Wb of a workpiece W in a noncontact state by a hydrostatic fluid. The thermal deformation prevention device 6 is used in a double-end surface grinding machine in which a thin disk-like workpiece W is rotationally supported with a workpiece rotationally supporting device 5, and a pair of high speed-rotating grinding wheels 1 and 2 are cut in the grinding wheel axis direction thereof and both surface and rear surface Wa and Wb of the workpiece W are simultaneously ground.. A heat shield plate 30 as thermal deformation prevention means for restraining the thermal deformation of the static pressure pads 15 and 16, is provided in a boundary part with the grinding wheels 1 and 2 in the static pressure pads 15 and 16.