To provide a numerically controlled machine tool equipment with an interpolating means capable of preventing the generation of folding points and polygonal lines at a high speed while preventing the working time from being prolonged by the increase of processing time at a command block.

This machine tool is provided with a command analytic means 4 for finding four continuous command positions including a command position commanded by the linear command of a program, a buffer 6 for storing the command positions, a 1st circular arc command calculating means 7 for finding a 1st three-dimensional(3D) circular arc command passed through three command positions on the front side, a 2nd circular arc command calculating means 8 for finding a 2nd 3D circular arc command passed through three command positions on the rear side, a circular arc selecting means 9 for selecting any one 3D circular arc command closest to the straight line passed through the command position of the linear command, and command replacing means 10 for replacing the linear command with the 3D circular arc command selected by the circular arc selecting means.