A base station apparatus is provided, by which a downlink transmission power can be properly set and frequent handovers of a mobile station (user equipment) can be prevented to occur. The base station apparatus is installed in a base station communicating with a mobile station in a mobile communication network, and provided with control means of controlling so as to decrease a setting of downlink transmission power when changing a setting of offset for handover from the own cell to a neighboring cell so as to advance a hand-out from the own cell to the neighboring cell.