The wireless base station 10 includes a multiplexing units 13 generating user data; a channel assignment control unit 14 for selecting subcarrier groups from a plurality of subcarriers on two carriers, forming two wireless frames including subchannels generated from the subcarrier groups, and time-division multiplexes and sets the user data and control data to the two wireless frames; and a transmitting and receiving unit 16 transmitting a wireless signal including the wireless frames, wherein the channel assignment control unit 14 divides all of the subchannels in the two wireless frames into areas of destination sectors, stores the control data only in the corresponding area, and stores the user data in all of the areas in the two wireless frames.