Values of the function includes the estimated life of the bearing supporting the main shaft control device

The numerical control apparatus of the present invention determines whether the spindle to cut the workpiece machining state, a state during cutting, and calculates the torque calculated from the feed axis corresponding to the force acting on the spindle multiplied by the weight of the spindle the speeds of the second and integrating the resultant value as an index, when not cutting state, the spindle speed for the index value integrating. In addition, the estimated life of the bearing according to the index value.