PURPOSE: To prevent the throughput of a communication controller from decreasing owing to a code converting process by instantaneously converting any code system without the intervention of a program.

CONSTITUTION: A memory 4 for transmitted data conversion converts the codes of transmitted data into the code system of the other party. A memory 5 for received data conversion converts the codes of received data into its code system. A communication control part 3 writes in data for code conversion in the memory 4 for transmitted data conversion and memory 5 for received data conversion according to composite information and controls a communication. A memory 2 is stored with the transmitted and received data. An arithmetic processing part 1 controls the whole communication controller.