A double side grinding device, comprising a pair of grinding wheels (4), a work rotating device (1), and a moving device (2), wherein each ground surface (4a) is brought into contact with a processed surface (a) on both sides of a work (W) so that the outer periphery of the work (W) crosses the outer periphery of each grinding wheel (4) and the center (c) of the work (W) is positioned inside each ground surface (4a) and is cut up to a specified position and, the cutting by each grinding wheel (4) is stopped and each grinding wheel (4) and the work (W) are moved, by the moving device (2), relatively in parallel with the processed surface (a) until the center (c) of the work (W) is disengaged from each ground surface (4a) so as to separate each ground surface (4a) from the processed surface (a), whereby both sides of a thin disk work can be ground simultaneously and easily by a small device, and also a variation in work thickness after grinding can be reduced.