PURPOSE: To disperse the loads of a communication processing part in a communication controller to circuit controlling parts by providing circuit connection parts with divided circuit controlling parts, and by performing circuit processing individually by using the circuit controlling parts.

CONSTITUTION: Data transfer between a large-amount communication controller in a figure, and an unshown central processor and a main storage device is controlled by an interface circuit 5, and the central processor and main storage device are connected via an input-output bus 6. The circuit controlling parts 7 which correspond to the circuit connection parts 1 are each started by the central processor with an instruction word which contains discrimination information correspondign to each circuit 2, and in accordance with a communication program stored in a storage part 4, the circuit controlling part 7 performs a series of operations. The time required for the processing of one character by the circuit controlling part 7 is equal to one-character time per circuit, so that a circuit speed can be increased.