<p>A numerical controller which controls the rotation of a plurality of spindles easily and at high speeds. The NC data produced from an NC data generated unit (1) include data for designating one or more spindles and data of splindle speed, and they are sent to switching means (2). Memories (3a to 3n) corresponding to the designated spindles are updated with the spindle rotation speed data by switching means (2), and rotations of the corresponding spindle motors (6a to 6n) are controlled based on the speed instructions from the updated memories (3a to 3n).</p>
