In human body communication, it is important to investigate the input impedance characteristics of electrodes and transmission characteristics between transceivers for improving the qualities of communication and reducing power consumption. In this work, we studied the input impedance characteristics and transmission characteristics between a wristwatch device and a handheld device using both a three-dimensional electromagnetic field simulation and experiment at 10 MHz. The input impedance and transmission characteristics obtained from the simulation using a muscle homogenous model and those obtained from the measurement using a muscle-tissue-equivalent phantom showed good consistency. The calculated electric field around a human arm decreased as it moved away from the surface of the arm. This distribution of the electric field showed the advantages of human body communication, which are confidential communication and electromagnetic compatibility (EMC). Moreover, power consumption at the feeding point of the system was calculated from the transmission characteristics obtained from the simulation. This result indicated that human body communication achieves low-power consumption.