A user apparatus in a mobile communication system including a first base station and a second base station that perform communication with the user apparatus by inter-base station carrier aggregation, including: a transmission trigger detection unit configured to detect a transmission trigger for transmitting uplink transmission power information in the user apparatus to the first base station or to the second base station; and an uplink transmission power information transmission unit configured to transmit the uplink transmission power information to the first base station or to the second base station based on a transmission trigger detected by the transmission trigger detection unit.