A mobile communication method comprising the steps of: causing a radio base station (eNB) to store combinations of LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C), said LTE network signaling values used for notifying a mobile station of a method of applying a reduction in a maximum allowable transmission power of the mobile station and corresponding to a band usable in carrier aggregation, and to store corresponding pieces of carrier aggregation band combination information (CA band combination #1, CA band combination #2), each of which specifying one of the combinations of LTE network signaling values and referring to a carrier aggregation band combination comprising said band usable in carrier aggregation; by a mobile station, notifying the radio base station (eNB) of a piece of carrier aggregation band combination information (CA band combination #1, CA band combination #2) that is supported by the mobile station among pieces of carrier aggregation band combination information (CA band combination #1, CA band combination #2) each of which specifies LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C), said notified piece of carrier aggregation band combination information referring to a carrier aggregation band combination comprising said band usable in carrier aggregation, and causing the radio base station (eNB) to determine to set carrier aggregation for the mobile station when all LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C) corresponding to said band usable in carrier aggregation and stored in the radio base station (eNB) are included in the LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C) specified by the received piece of carrier aggregation band combination information (CA band combination #1, CA band combination #2). causing a radio base station (eNB) to store combinations of LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C), said LTE network signaling values used for notifying a mobile station of a method of applying a reduction in a maximum allowable transmission power of the mobile station and corresponding to a band usable in carrier aggregation, and to store corresponding pieces of carrier aggregation band combination information (CA band combination #1, CA band combination #2), each of which specifying one of the combinations of LTE network signaling values and referring to a carrier aggregation band combination comprising said band usable in carrier aggregation; by a mobile station, notifying the radio base station (eNB) of a piece of carrier aggregation band combination information (CA band combination #1, CA band combination #2) that is supported by the mobile station among pieces of carrier aggregation band combination information (CA band combination #1, CA band combination #2) each of which specifies LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C), said notified piece of carrier aggregation band combination information referring to a carrier aggregation band combination comprising said band usable in carrier aggregation, and causing the radio base station (eNB) to determine to set carrier aggregation for the mobile station when all LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C) corresponding to said band usable in carrier aggregation and stored in the radio base station (eNB) are included in the LTE network signaling values (NS_X, NS_Y, CA_NS_A, CA_NS_B, CA_NS_C) specified by the received piece of carrier aggregation band combination information (CA band combination #1, CA band combination #2).