To improve signal transmission gain in human body communication.

A transmitter 1 includes a transmitting side data processing portion 11 for generating communication information which is an information to be transmitted to a receiver 2, a modulator 12 for modulating the communication information to output a transmit signal, a transmit electrode 13 for impressing the transmit signal outputted by the modulator 12 onto a human body 3 and inducing an ac electric field around the human body, and an inverting circuit 14 for inverting positive/negative of the transmit signal outputted by the modulator 12 to output an inverted transmit signal. In addition, the inverted transmit signal outputted by the inverting circuit 14 is impressed onto an earth side electrode 4 connected with earth ground capacitively coupled to the human body 3. When a hand of the human body 3 carrying the transmitter 1 is held upon the transmit electrode 13, the transmit electrode 13 is capacitively coupled to the human body hand, and impress an ac voltage by the transmit signal onto the human body hand. On the other hand, the receiver 2 detects the ac electric field induced around the human body.