In a bus arbitration method and bus arbiter which simultaneously considers fairness and priority and enables fairness and priority to be readjusted by a program, that is, by software, arbitration for ownership of a bus connected to a plurality of bus masters comprises grouping the plurality of bus masters into a plurality of groups and arbitrating the frequency of each bus master's ownership of the bus according to the result of the grouping. It is preferable that each of the plurality of groups has a priority different from the priorities of the others, and in arbitrating the frequency of each bus master owning the bus, arbitration of ownership of the bus by bus masters belonging to the same group is performed according to a round-robin method.