A numerical controller includes a position instruction generating unit configured to generate the position instruction; an oscillation instruction generating unit configured to generate the oscillation instruction; a position speed control unit configured to add the position instruction and the oscillation instruction to generate a synthesized instruction; and a current control unit configured to control movement of a tool or rotation of a spindle. The oscillation instruction generating unit includes a tracking error calculating unit configured to obtain and calculate an actual angle and an ideal angle of the spindle, and a frequency recalculating unit configured to recalculate the oscillation frequency or a rotational speed of the spindle based on the actual angle and the ideal angle. The current control unit controls the movement of the tool or the rotation of the spindle according to the recalculated oscillation frequency or rotational speed of the spindle.