A radio communication system for a vehicle which allows communication not only between a driver and a passenger of one vehicle but also with a driver or a passenger of another vehicle without increasing the scale of a radio communication apparatus to be mounted on a helmet. A radio wave signaled from a radio wave transmitter-receiver of a driver or a passenger of a vehicle is received by a repeating apparatus of the self-vehicle and amplified by and re-signaled from the repeating apparatus. The radio wave signaled from the repeating apparatus is received by a radio wave transmitter-receiver of a driver or a passenger of another vehicle and reproduced by a speaker. A radio wave signaled from the radio wave transmitter-receiver of the driver or a passenger of the vehicle is received by a repeating apparatus of the self-vehicle and amplified by and re-signaled from the repeating apparatus. The radio wave signaled from the repeating apparatus is received by the radio wave transmitter-receiver of a driver or a passenger of the vehicle and reproduced by a speaker.