The apparatus enhances the degree of freedom in communication using a quasi-electrostatic field. A card device 3 (a ticket checking and collecting machine 2) side in a communication system 1, a quasi-electrostatic field according to an identification signal S5 (a notification signal S9) modulated according to identification information S4 (notification information S8) is generated from an internal electrode 8 (a side-surface electrode 7) to electrify a human body. At the ticket checking and collecting machine 2 (the card device 3), displacement of the strength of a information-transmission quasi-electrostatic field DTD which is isotropically formed in the neighborhood of the human body is detected via the side-surface electrode 7 (the internal electrode 8) and a FET 28 (a FET 37) sequentially, and based on the detection result, the identification information S4 (the notification information S8) is demodulated. Sending and receiving of information without directional restrictions in the neighborhood of the human body, freedom in communication can be enhanced.