To provide a numerical control machine tool precision inspection device which enables automatic measurement of precision of a machine tool by any worker other than highly skilled worker.

A controlling personal computer 5 receives an external output signal of a numerical control device 7, the controlling personal computer 5 outputs a change-over signal to a gage head selector 3 so that the result of measurement from a gage head 2a or 2c which corresponds to the external output signal is sent to an electrical micrometer 4, and the measured value from the electrical micrometer 4 is read, recorded, and output by the controlling personal computer 5 to output an external input signal for the numerical control device 7. Consequently, the precision of a numerical control machine tool is measured automatically.