A broadband radio communication system and method therefore that conducts communication on a plurality of narrowband channels obtained by dividing a broadband channel into a plurality of narrowband channels. The invention provides a first radio communication terminal which sets transmission conditions of at least part of the narrowband channels and transmits a wireless packet on the narrowband channels of which the transmission conditions have been set, and a second radio communication terminal which receives the wireless packet from the first radio communication terminal, measures the line qualities of the narrowband channels and transmits measured line quality information to said first radio communication terminal. The first radio communication terminal receives the line quality information, sets new transmission conditions based on the line quality information, and transmits a wireless packet to the second radio communication terminal through the narrowband channels under the new transmission conditions.