To provide a radio base station apparatus, a radio relay station apparatus and a resource allocation method each which perform resource division of a backhaul sub-frame more optimally and can improve a throughput of a system, in the case of relay transmission. The radio base station apparatus according to the present invention includes: a frequency bandwidth control section configured to control a frequency bandwidth in a backhaul sub-frame, based on the number of the backhaul sub-frames, the number of mobile terminal devices, and frequency utilization efficiency of a radio link; and a transmitting section configured to transmit the backhaul sub-frame with the frequency bandwidth controlled by the frequency bandwidth control section.