A numerical control device used for a machine tool and configured to move a machining tool and a workpiece in the same direction on parallel respective drive shafts based on a machining program and control a relative positional relationship between the machining tool and the workpiece during the motion in the same direction, at least one of motion instructions for the machining tool and the workpiece being an instruction whose instruction value varies arbitrarily with time elapsed, includes: a machining program analysis unit that acquires the motion instructions for the machining tool and the workpiece from the machining program; a motion instruction generation unit that generates machining tool motion instruction data on the machining tool and workpiece motion instruction data on the workpiece based on the motion instructions; and an interpolation unit that generates machining tool interpolation data based on the machining tool motion instruction data and generates workpiece interpolation data based on the workpiece motion instruction data.

Provided is a machine tool control device that can generate movement commands of any required command form and that can also suppress the deviation of a peak position during air cutting. A machine tool control device 1 that performs processing while making a tool and a workpiece oscillate relative to each other. The machine tool control device 1 comprises an oscillation conditions setting unit 11 that sets oscillation conditions, an oscillation phase division unit 12 that divides an oscillation phase into a plurality of segments, a layered command calculation unit 13 that, for each of the divided segments, calculates a layered command as a movement command on the basis of the oscillation conditions, and a position and speed control unit 17 that makes the tool and the workpiece oscillate relative to each other on the basis of the layered commands.