Abstract: A numerical controller having a memory device for storing a profiling program composed of a series of data blocks, each of which designates an incremental rotational amount of an oval workpiece and an incremental feed amount of a tool slide, and a digital computer for reading out the data blocks one by one from the memory device when no rough grinding is instructed, so as to provide, based upon a read-out data block, interpolation data of feed pulses which are to be distributed for tool slide feed in connection with feed pulses to be generated for workpiece rotation. In rough grinding, the digital computer reads out a predetermined number of the data blocks and accumulates profiling data included therein so as to provide interpolation data based upon the accumulated profiling data, thereby shortening processing time for providing the interpolation data in rough grinding.