Abstract: Disclosed is an adapter for grinding machine comprising: a grinding shaft sleeve of cylindrical shape whose one end is open and having at least one through hole formed at a selected position of an outer circumference; a grinding shaft rotatably and movably fitted in the grinding shaft sleeve, the grinding shaft including at least one guide groove having a variable surface curvature with respect to a shaft direction and formed at a position corresponding to the through hole, the grinding roller being installed at one end of the grinding shaft and a rotational force generating unit being installed at the other end of the grinding shaft; a grinding shaft stroke unit whose one end is coupled to the through hole of the grinding shaft sleeve and the other end is fitted in the guide groove, for stroking the grinding shaft with the grinding shaft sleeve; a sealing means interposed between an outer circumference of the grinding shaft and the grinding shaft sleeve, for preventing leakage of oil; and a sealing cover cou