A data communication system includes a transmission medium such as a human body for transmitting an information signal via an electric field, a mobile device including a sender for imparting the electric field in which the information signal is modulated to the transmission medium, a stationary device including a receiver for detecting the electric field via the transmission medium and demodulating the electric field into the information signal, a floor cover arranging the stationary device and also being contacted by the transmission medium, in which the floor cover has a communication area contacted by the transmission medium where a data communication is performed between the mobile device and the stationary device, and the communication area is in a state of being electrically floating with respect to the floor cover.