To provide a device capable of simultaneously and easily grinding both surfaces of a thin disk-shaped work piece and capable of being downsized.

A double surface grinding device is provided with a pair of grinding wheels 8, 9, and a work piece rotating device for supporting and rotating a work piece W so that the machining surfaces (b) of both surfaces of the work piece W may face the circular grinding surfaces of the grinding wheels 8, 9 and a part of the outer periphery of the work piece W and the center (c) may be positioned inside the outer peripheries of the grinding wheels. The work piece rotating device is, provided with a pair of position holding belts 21, 22 for pinching a part of the work piece W projecting from between the grinding wheels 8, 9 from both sides in the radial direction and for moving it in the circumferential direction of the work piece W, grooves 23 for supporting the work piece W in the axial and radial directions by fitting the outer periphery of the work piece W are provided on respective belts 21, 22, and at least one of the belts 21, 22 is a driving belt for rotating the work piece W by being rotated in the circumferential direction of the work piece W.