To provide a radio communication system capable of quickly acquiring emergency information by a roadside communication device.

The radio communication system includes a plurality of roadside communication devices 2. Each roadside communication device 2 includes a communication control unit for acquiring transmission information to be transmitted to a vehicle and for radio transmitting the acquired transmission information to the vehicle. When transmitting emergency information i.e. information related to an emergency state, the communication control unit radio transmits the emergency information by BPSK, a modulation scheme having a lower transmission rate than 16QAM which is a modulation scheme for use when transmitting transmission information other than the emergency information.