A mobile communication system in which a base station apparatus and a mobile station apparatus are adapted to communicate using a plurality of component carriers, comprising: the base station apparatus configured to transmit, in a sub frame to the mobile station apparatus, a plurality of physical downlink control channels on a first downlink component carrier and a plurality of physical downlink control channels on a second downlink component carrier, one of the plurality of physical downlink control channels on the first downlink component carrier being for indicating transmission of a physical downlink shared channel on a third downlink component carrier being different from the first downlink component carrier and the second downlink component carrier, another one of the plurality of physical downlink control channels on the first downlink component carrier being for indicating transmission of a physical downlink shared channel on the first downlink component carrier, one of the plurality of physical downlink control channels on the second downlink component carrier being for indicating transmission of a physical downlink shared channel on a fourth downlink component carrier being different from the first downlink component carrier, the second downlink component carrier, and the third downlink component carrier, and another one of the plurality of physical downlink control channels on the second downlink component carrier being for indicating transmission of a physical downlink shared channel on the second downlink component carrier, the mobile station apparatus configured to transmit, to the base station apparatus, first control information on HARQ using one of a first plurality of physical uplink control channel resources, and second control information on HARQ using one of a second plurality of physical uplink control channel resources, each of the first plurality of physical uplink control channel resources corresponding to a resource of any one of the plurality of physical downlink control channels on the first downlink component carrier, and each of the second plurality of physical uplink control channel resources corresponding to a resource of any one of the plurality of physical downlink control channels on the second downlink component carrier, wherein the first plurality of physical uplink control channel resources are mapped on a first uplink component carrier that corresponds to the first downlink component carrier, and the second plurality of physical uplink control channel resources are mapped on a second uplink component carrier that corresponds to the second downlink component carrier. the base station apparatus configured to transmit, in a sub frame to the mobile station apparatus, a plurality of physical downlink control channels on a first downlink component carrier and a plurality of physical downlink control channels on a second downlink component carrier, one of the plurality of physical downlink control channels on the first downlink component carrier being for indicating transmission of a physical downlink shared channel on a third downlink component carrier being different from the first downlink component carrier and the second downlink component carrier, another one of the plurality of physical downlink control channels on the first downlink component carrier being for indicating transmission of a physical downlink shared channel on the first downlink component carrier, one of the plurality of physical downlink control channels on the second downlink component carrier being for indicating transmission of a physical downlink shared channel on a fourth downlink component carrier being different from the first downlink component carrier, the second downlink component carrier, and the third downlink component carrier, and another one of the plurality of physical downlink control channels on the second downlink component carrier being for indicating transmission of a physical downlink shared channel on the second downlink component carrier, the mobile station apparatus configured to transmit, to the base station apparatus, first control information on HARQ using one of a first plurality of physical uplink control channel resources, and second control information on HARQ using one of a second plurality of physical uplink control channel resources, each of the first plurality of physical uplink control channel resources corresponding to a resource of any one of the plurality of physical downlink control channels on the first downlink component carrier, and each of the second plurality of physical uplink control channel resources corresponding to a resource of any one of the plurality of physical downlink control channels on the second downlink component carrier, wherein the first plurality of physical uplink control channel resources are mapped on a first uplink component carrier that corresponds to the first downlink component carrier, and the second plurality of physical uplink control channel resources are mapped on a second uplink component carrier that corresponds to the second downlink component carrier.