The processing circuit of an inter-vehicle communication device includes a transmission output correction table in which a transmission power value or a corrected transmission power value in accordance with propagation characteristics of radio waves transmitted from an own vehicle is set to correspond to a region with coordinates having a direction of travel of the own vehicle as an axis. The processing circuit acquires a transmission power value or a corrected transmission power value corresponding to relative position coordinates of a peripheral vehicle from the transmission output correction table, and determines transmission power for when transmitting own vehicle travelling information to the peripheral vehicle. Because of this, communication with the peripheral vehicle positioned in a region in which radio wave propagation characteristics are sparse can be reliably established, and communication congestion can be avoided.