Abstract: A numerical control apparatus can process a workpiece at high speed and high precision while suppressing tool abrasion by maintaining optimum cutting conditions determined by a combination of spindle rotational speed and tool feed speed. A spindle rotational speed control section changes the speed of the spindle according to a tool feed speed obtained by a tool feed speed deciding section based on the shape of the tool moving path commanded by a machining program. Alternatively, the spindle rotational speed is changed by a spindle rotational speed control section based on a change in the contact position between the tool and the workpiece to be cut in the tool axial movement direction. Further, the spindle rotational speed may be changed by the spindle rotational speed control section based on the tool feed speed including tool axial movement direction data obtained by a feed speed deciding section based on the shape of the tool moving path.