PURPOSE: To set a dressing angle quickly, accurately and precisely by setting a given angle gauge between the side plate of the bed of a grinding machine and a contact plane to a side plate installed on a base plate with respective to a desired dressing angle.

CONSTITUTION: An angle gauge AG is set between the side plate 3 of the bed 2 of a grinding machine and a reference plane 1 provided on a base plate 4 with respect to a desired dressing angle. A dressing device D is fixed to the bed 2 by electrifying a magnet bed MB and a motor holder 6 is fixed at a middle position along the stroke S of the base plate 4 with a fixture 13, so that an operating device for the bed 2 of the grinding machine may be operated to set a dressing grinding wheel 11 and a dressed grinding wheel 14 in place. The fixture 13 is released, a motor 7 is activated, an automatic mover for the bed 2 of the grinding machine is started and a handle 12 is operated forward and backward for dressing. In this way, more efficient work can be done, resulting in higher productivity.