To provide a radio transmission apparatus capable of suppressing such switching of a modulation system as can occur just after restoration of abnormal state in one system, and avoiding unwanted degradation of circuit band.

The radio transmission apparatus has a redundant configuration including an active system and standby system, and is such modulation system switching type as performing modulation system switching control in synchronous with the cycle signal of radio transmission frame in which the radio circuit quality is monitored on a demodulation side, and switching is made for a modulation system of multivalent low when the circuit quality degrades, but when the circuit quality improves, switching is made for a modulation system of multivalent high. The radio transmission apparatus (1a) includes means which detects transition of state caused by releasing of alarm issue by a modulation/demodulation circuit (14a) and holds the detected alarm state until a preset time period expires (modulation system determination circuit 16a), and means which invalidates determined multivalent information of a system in which the alarm state continues and selects determined multivalent information of a system in which no alarm is issued (modulation system determination circuit 16a).