PURPOSE: To correctly shift the specified location of an image by calculating the position difference value of a cursor, obtaining the start point and the end point of data to be displayed and shifting.

CONSTITUTION: A main processor 1 reads a program or a parameter, etc., stored in ROM or RAM 3 and implements a graphic operation. That is, three- dimensional data of a mobile object is defined, the data is scaled so as to meet the size of a CRT screen and data to be displayed in CRT is obtained. Then, the main processor 1 reads the center value of the object stored in RAM 3 and performs scaling so as to be illustrated with the CRT screen as a center. The object center value apart from the center value of the CRT screen is obtained, one of the shift locations, etc., of a graphic is designated, the difference value of a shift part position and a shift position, the start point and the end point of a line and an arch, etc., on the CRT screen are obtained and the line and the arch, etc., are interpolated so as to be displayed in CRT.