PURPOSE: To achieve high speed access to an image memory by providing an image processor with a cache memory dedicated to the image memory, and executing reading/writing to the image memory with respect to the cache memory.

CONSTITUTION: High speed reading/writing to the image memory 1 is achieved by providing the image processor with the cache memory 2 dedicated to the image memory, which has the copy of a part of the image memory 1. When data is written in the cache memory 2, a cache control means 15 transfers image data stored in the cache memory 2 to the image memory 1 in response to a transfer signal outputted from a rewriting timer means 14 at every interval. Thus, the rewritten image data is not stored in the cache memory 2 until it is selected as the object of the replacement. Thus, high speed access to the image memory 1 can be obtained without deteriorating the natural property of displaying.