To save a CNC image that fetches data held by a host computer (called a host below) and/or data held by a CNC device (numeric controller) on the side of the host and to display it on the CNC device.

This device decomposes display items of a CNC image into elements such as characters, graphics, data that is held by a host 10 and data that is held by a CNC device 20, specifies the display position, display content and form of the data on the CNC image and saves them as CNC image data in an auxiliary storage device 13. When the device 20 makes a CNC image request through a communication network 30, the host 10 sends the CNC image data and shows it on a CRT 24 of the device 20. In such cases, a part which designates data that is held by the host 10 fetches the real data, sends it and shows it. Also, a part which designates data that is held by the CNC device fetches the real data and shows it. Further, these data are updated in every prescribed cycle.