A numerical control apparatus includes a command argument determination unit which determines whether a vector is included in an argument of a circular arc interpolation command which is included in command data and a circular arc shape forming unit which forms a circular arc shape based on a machining program, and a start point, an end point, and the vector, which are specified by the argument of the circular arc interpolation command, when the command argument determination unit determines that the vector is included in the argument of the circular arc interpolation command.