A radio base station apparatus including a function for determining a transmission power, including: a neighbor cell detection unit configured to detect a neighbor cell that interferes with a target cell that the radio base station apparatus can form; a received power measurement unit configured to measure, for each neighbor cell detected by the neighbor cell detection unit, a received power from the neighbor cell; and a transmission power determination unit configured to calculate, for each band part that overlaps with a transmission band of the radio base station apparatus in transmission bands of each neighbor cell, a sum of received powers for neighbor cells having transmission bands each including the band part, and to determine an interference amount in the target cell based on the sum of received powers so as to determine the transmission power by using the interference amount.