A data communication system includes an information acquiring unit and a selector. The information acquiring unit acquires positional information of a third party capable of detecting data communication performed between communication bodies, positional information of each of the communication bodies, and terrain information. The selector selects a fourth communication body from third communication bodies when transmission of transmission data from a first communication body to a second communication body out of the communication bodies is not successful. The third communication bodies are remaining communication bodies out of the communication bodies excluding the first and the second communication bodies and successful in receiving the transmission data from the first communication body. The fourth communication body is lowest in a possibility that the data communication is detected by the third party out of the third communication bodies, and transmits the transmission data to the second communication body.