The present invention provides a method of computing a correction value for the machine tool having two or more translational axes and one or more rotational axes for correcting error in a position and an orientation of the tool with respect to a workpiece due to the geometric error. The method includes a rotational axis correction value computing step (S3) for computing a correction value for the rotational axis by use of a geometric parameter representing the geometric error, and a translational axis correction value computing step (S4) for computing a correction value for the translational axis by use of a command value for each of the rotational axes, a command value for each of the translational axes, and the geometric parameter.