To provide a radio base station apparatus that enables the effect of improving usage efficiency of radio resources to be exerted sufficiently also in the case where the number of user terminals multiplexed into the same radio resources further increases, the radio base station apparatus performs communications using a first resource region for a downlink control channel subjected to time division, and a second resource region for a downlink data channel, and is characterized by being provided with generation sections (307, 308) that generate a first notification signal for notifying of the number of OFDM symbols of the first resource region, and a second notification signal for notifying of a starting position in the time domain of a third resource region obtained by performing frequency division on a part of the second resource region, and a multiplexing section (312) that multiplexes the first notification signal into the first resource region, and the second notification signal into the third resource region.