PURPOSE: To execute request arbitration having high throughput without forming a gap between requests.

CONSTITUTION: A priority determining circuit in a multi-processor system receives requests from respective processors and arbitrates the competition of these requests. The requests from respective processors are inputted to a fixed priority circuit 420 through a selector 410. The circuit 420 selects only one request and the selected result is stored in an output register 430. The stored request is detected by an AND circuit 450 and the detected result is stored in a holding register 440. When the request stored in the register 440 exists, a succeeding request is not selected by the selector 410. On the other hand, plural fixed priority circuits 420 in the multi-processor system can determine mutually different priority values in accordance with the using situation of the system.