To easily display an image area to be observed when the same image area is repeatedly observed by providing a means which selects the area of the display image data to be stored in a 2nd memory means among temporarily stored image data.

A window memory 84 expands display image data on a CRT among image data in a 1st memory means in two dimensions and temporarily stores them. A data area selection part 80 selects the area of image data to be stored in the window memory 84 among the image data to be stored temporarily in the 1st memory means. An image scroll part 202 outputs an area select signal to a data area selection part 80 according to the coordinates of the area of the image data registered in an area coordinate storage part 200 of the image data in the window memory 84 to select the area of the data of the display image to be stored in the window memory 84 among the image data which are expanded in the 1st memory means in two dimensions and stored temporarily.