PURPOSE: To provide the image processor equipped with optimum throughput to image processing contents at all times.

CONSTITUTION: An image memory 56 is provided with memory elements 32, 34, 36 and 38 to store and independently read/write image data, and a base processor unit 12 is provided with processor elements 16, 18, 20 and 23 to process the image data stored in the correspondent memory elements corresponding to the respective memory elements. Further, more than one freely attachable and detachable accel processor units 14 are provided with processor elements 24, 26, 28 and 30 to individually process the image data stored in the correspondent memory elements in cooperation with the correspondent processor elements corresponding to the processor elements of the base processor unit 12, and a processor unit number recognizing means is provided to recognize the number of the mounted processor units.