To improve the use rate of a bus by permitting an allocation means to allocate a right for using the common bus by means of respective units in terms of decision theory.

A central controller 20 issues operation commands in a slot (prescribed time interval) unit to a storage part 4 and a network part 6 and Writes the program of a micro schedule into a micro schedule table 22. A micro scheduler 24 definitely controls the use of the common bus YBUS by the storage part 4 and the network part 6 in accordance with the program. Namely, the bus use periods of the respective units are definitely guaranteed not by mediating a bus use right from the respective units but allocating the bus use right by the previously decided micro schedule.