To efficiently use a bus even when a bus master of priority higher than the bus master of a bus right requesting destination exists.

A bus using period by a second bus master 4 of priority higher than the first bus master 1 of the bus right requesting destination and a maximum bus using predicted period using the bus right obtained from the first bus master 11 are added. Thus added period is subtracted from a bus using cycle by the second bus master 4 and the remaining period is made the effective period (Td) of a bus right request to the first bus master 11 and the starting point of an effective period is matched with the use termination point of the bus by the second bus master 4. As this starting point is also the bus non-using period of the second bus master 4, a bus right obtained once is not parted with and the efficiency of bus usage is not damaged.