An information processing device that generates a first NC program used by a machine tool, said information processing device being provided with: an NC program interpretation unit for interpreting each of a plurality of codes included in a second NC program; an inverse conversion unit for inverse-converting the second NC program on the basis of the interpretation by the NC program interpretation unit, and generating an automatically programmed tools (APT) program written in APT; and a conversion processing unit for analyzing the APT program and reconverting said program to a first NC program in which additional code corresponding to starting code contained in the second NC program has been added.