An on-board wireless device used in a subject vehicle and transmitting a vehicle information of the subject vehicle to a periphery vehicle positioned around the subject vehicle, includes a transmitting circuit successively transmitting the vehicle information of the subject vehicle via a vehicle-to-vehicle communication at a transmission interval, a transmission interval setting section setting the transmission interval that is variable for transmitting the vehicle information, and a generation section generating the vehicle information to be transmitted by the transmitting circuit. The generation section includes, in the vehicle information, a transmission interval related information based on which the transmission interval set by the transmission interval setting section is specified. The transmitting circuit transmits the vehicle information that includes the transmission interval related information to the periphery vehicle.