PURPOSE: To have automatic grinding using simple device by performing locational control of a grinding tool using contour tracing means equipped with a horizontally revolving arm, carrying out then grinding of the end face, and by controlling the grinding pressure by reference to the entered data.

CONSTITUTION: A glass sheet 1 to be used as a windshield of a car, for ex., is supported on a basis 3 equipped with a pair of suction cups 2a, 2b, and a rotary grinding wheel 4 is pressed to the end face to make end-face grinding such as chamfering. The grinder unit 5 consisting of said grinding wheel 4 and a drive motor is moved along the contour of the glass sheet 1 by a single joint type robot 6 consisting of shafts θ1Wθ3, horizontal revolving arms 60, 62, a joint 61, wherein the data about this contour is previously stored in a robot control part. The location of said grinder unit 5 and the grinding pressure of the wheel 4 are controlled on the basis of numerical control data prepared in correspondence to this data about contour.