The information processing device comprises first and second master circuits and an arbiter for arbitrating access rights to a bus to which the master circuits are connected. The arbiter has storage units retaining information representing priorities of the access rights, and an arbitration control logical unit for arbitrating the access rights of the master circuits based on the information. When the priority of the first master circuit is higher than the priority of the second master circuit and there is no access request from the first master circuit but there is an access request from the second master circuit, the arbitration control logical unit permits access of the second master circuit, and the storage units lower the priority of the second master circuit without changing the priority of the first master circuit.