A work having a portion to be ground, such as a tapered surface, is ground by a grinder driven by a driving device. During grinding operation, coolant is supplied to a grinding surface of the grinder and the portion to be ground. After the grinding operation is completed, the coolant is continued to be supplied for removing sludge on the grinder while the grinder is leaving the work and returning to its original position. The coolant may be pressurized to a higher level when it is supplied for removing the sludge than when it is supplied during the grinding operation. The number of works that have been already ground may be counted, and the coolant for removing the sludge may be supplied only when the number of works exceeds a predetermined number. Alternatively, the sludge is removed by brushing when the number of works does not reach the predetermined number.
