A radio transmitter/receiver having a QoS control unit for outputting the transmission data in order taking the quality of service (QoS) into consideration. In the case where the information transmission rate for a radio section is not lower than a threshold value, the QoS control operation of the transmission data is omitted, and the transmission data are output in the order of input. In the case where the information transmission rate for the radio section is lower than the threshold value, on the other hand, the QoS control mode is switched in accordance with the information transmission rate for the radio section.