In an in-vehicle radio apparatus to radio-transmit information from a vehicle about to enter an intersection, the interference between a radio signal transmitted from the vehicle and a radio signal transmitted from another vehicle is suppressed. Further, an approach direction of the vehicle to the intersection can be accurately transmitted. In the radio apparatus to transmit a radio signal by using a spread spectrum method, it is determined that the vehicle has approached a first distance from the intersection, and based on the determination, a spread code corresponding to an approach direction of the vehicle to the intersection is allocated as a spread code used for transmission.