A numerical control device including tapping spindle (S1, S2) time constant selecting means that compares acceleration and deceleration time constants of the S1 and S2 axes and selects the larger time constant, drilling axis (X1) acceleration and deceleration processing means that calculates an acceleration and deceleration movement amount of the X1 axis based on the selected spindle time constant and a commanded spindle rotation number and moves the drilling axis to the calculated position, synchronized tapping interpolation processing means that synchronizes the tapping spindle with the drilling axis based on the movement amount output from the drilling axis (X1) acceleration and deceleration processing means and a pitch, and tapping spindle synchronization processing means that transfers the rotation amount of the tapping spindle output from tapping spindle (S1)-drilling axis (X1) synchronization processing means to the synchronized side.