PURPOSE: To eliminate a cutting error due to tool wear and to cut with a high accuracy, by equipping a wear correction means which corrects the position of a tool according to a work program with its reading of the wear quantity to the cutting distance of a tool from a tool wear quantity memory.

CONSTITUTION: A driving control part 8 feeds out to a driving mechanism 9 the rotation control signal which rotates a workpiece 2 in the A direction by the specific rotation number with the command of an NC control part 5, shows the position of a bite 1 by a work program and also feeds out to the mechanism 9 the position control signal which moves the bite 1 in the B direction at the specific speed. The mechanism 9 rotates the workpiece 2 in the A direction by receiving a rotation control signal, moving the bite 1 to the position followed by the work program by receiving the position control signal, moving the bite 1 in the B direction as well and cutting the workpiece 2. While under this cutting the control part 5 finds the cutting distance of the bite 1, reading the wear quantity to the cutting distance from a tool wear quantity memory 7. The control part 5 then corrects the tool position of the work program with this wear quantity and feeds it to a control part 8.