Provided is a radio base station apparatus capable of transmitting a control signal efficiently even in radio communications using a system band that includes a plurality of component carriers. In the radio base station apparatus, control signals of transport blocks corresponding to the plural component carriers are coded jointly and the coded control signal is assigned to one or plural component carriers to be transmitted. A mobile terminal apparatus receives data from the radio base station apparatus, separates the control signal from the received data and decodes the separated control signal thereby to obtain control information of the transport blocks of the corresponding component carriers.