A mobile device, a base station device, and a transmission rate control method for preventing the reception power at all the base station devices of an active set from exceeding an RoT threshold and preventing an excessive load. A transmission rate command acquiring section (304) of the mobile station device (300) acquires transmission rate commands transmitted from the base station devices (100a to 100c) from a received signal. A transmission rate determining section (305) determines the transmission rate of the uplink channel according to the transmission rate command. A DOWN monitoring section (306) monitors the transmission rate command from the base station devices (100b, 100c) of a non-primary cell and monitors the amount of “DOWN”. The DOWN monitoring section (306) judges that the load is heavy in a base station device where the amount of “DOWN” is large. If there is a base station device where the load is heavy, an another-cell load information creating section (307) creates another-cell load information for inhibiting creation of AG by the base station device (100a ) of the primary cell.