The utility model relates to a grinding wheel dresser for circular grinding machines. The utility model which comprises a dressing tool, a base and a numerical control system, wherein, the base is arranged on a worktable of the grinding machine, and a rotary disc is arranged on the base. The numerical control system controls a servo motor A to drive the rotary disc to rotate. The dressing tool is arranged on the rotary disc, can directly dress grinding wheels, and the center of circle of a circular arc of the cutting edge of the dressing tool is positioned in the axial lead of rotation of the rotary disc. Because the dressing tool of the utility model can backwards, forwards, leftward and rightward move correspondingly to the grinding wheels, and can rotate around the center of circle of the circular arc of the cutting edge of the dressing tool, the utility model can accurately dress the grinding wheels of various curve faces, and additionally has the advantages of convenient manufacture, low cost, high efficiency and easy realization of numerical control programming.