A user apparatus in a mobile communication system in which carrier aggregation is performed using a plurality of cells is disclosed. The user apparatus includes a processor that determines whether a physical uplink shared channel (PUSCH) is set in the user apparatus at a transmission timing of uplink control information, and determines to transmit the uplink control information by using the PUSCH when the PUSCH is set. The user apparatus also includes a transmitter that transmits the uplink control information to a radio base station using the PUSCH. The processor determines, when a PUSCH is set in a first cell in the plurality of cells, to transmit the uplink control information using the PUSCH. When no PUSCH is set in the first cell, the processor determines to transmit the uplink control information using a PUSCH in a second cell.