PURPOSE: To improve work efficiency by accelerating processing based on image data by easily transferring the image data to respective positions in a short time while using a communication line network by providing plural compressing/ extending elements corresponding to one frame memory and performing compression processing with the respective compressing/extending elements.

CONSTITUTION: An image compressing/extending device 20 is provided with four compressing / extending elements 25-28 and four buffer memories 31-34 corresponding to one frame memory 21. Then, the image data just for one frame converted into digital signals by an analog/digital converter 15 are written in the frame memory 21 of the image compressing/extending device 20. Thus, since the image data just for one frame are compressed by using four compressing/extending elements 25-28, the amount of data to be processed by one compressing/extending element is reduced, and the time required for compressing all the data stored in the frame memory 21 can be shortened to almost 1/4.