An object of the present invention is to provide a roadside communication apparatus and an in-vehicle communication apparatus capable of reducing an increase in a traffic amount in a roadside-to-vehicle communication. A roadside communication apparatus according to the present invention includes: an inter-vehicle transmission-and-reception service processing unit transmitting and receiving a roadside-to-vehicle message and an inter-vehicle message; a communication transfer unit providing a transaction service and a transfer service; a roadside-to-vehicle application processing unit; an inter-vehicle application processing unit; a transmission-and-reception condition management unit managing a transmission-and-reception condition of an inter-vehicle message which the inter-vehicle application processing unit transmits to and receives from the communication device; and a roadside communication management unit managing a connection state with the communication device, wherein the roadside communication management unit manages a connection state with the communication device based on a reception condition of the inter-vehicle message notified by the transmission-and-reception condition management unit.