Abstract: A grinding machine control apparatus comprises revolution speed changing means effective to selectively change a high speed in the grinding or a low speed in the dressing operations, a change signal generating means to generate a dressing initiation signal after the lapse of a predetermined time after a grinding wheel spindly driving motor is turned off, and control means to change said revolution speed changing means in response to a change signal from said change signal generating means and operative to drive a driving motor of a grinding wheel at a predetermined low speed of revolution. In a high-speed grinding machine, the speed of revolution of a grinding wheel spindle is automatically changed to reduce from a high revolution speed in the grinding operation to a low speed in the dressing operation without stopping a grinding wheel spindle so that a dressing operation can be carried out with good efficiency and a grinding wheel profile accuracy is substantially improved.