PURPOSE: To execute processing at a high speed at the time of accessing image data of a picture element being adjacent to a picture element set in advance.

CONSTITUTION: An address of image data to be accessed is set in advance to D flip-flops 17, 18 for setting an address. Subsequently, to monadic adder/ subtracters 20, 21 for converting an address, how the address is converted at the time of converting the address is set, and an address of a picture element set to the D flip-flops 17, 18 for setting the address is converted automatically to an address of a picture element being adjacent thereto. Thereafter, under the control of a control circuit 13, the image data of the converted address is accessed to an image memory 11. By repeating the abovementioned processing, while switching successively operation modes (access modes) of the monadic adder/subtracters 20, 21, the image data of the adjacent picture element is accessed successively.