Abstract: A numerical controller for an angular slide grinding machine capable of controlling movement of a work table with a dressing tool in a machine coordinate system in a dressing operation and a workpiece coordinate system in a grinding operation. When the work table is initially moved to such a position as to bring the dressing tool into slight contact with an end surface of a grinding wheel carried by a wheel head, the numerical controller calculates and stores a dressing reference value indicating a positional relation between a fixed machine origination position and the dressing tool in the machine coordinate system. Prior to grinding operations for each workpiece, the work table is moved under the control of a sizing device to such a position as to present a reference surface of the workpiece to a predetermined positional relation with the original machine position.