A communication device for communicating with an external device using a human body as a signal transmission path, includes an electric field strength measuring unit configured to measure a noise level from a detected received electric field strength at the time of no signal after the received electric field strength is detected by the communication device when a transmission signal to be output to the external device is absent, a transmission output determination unit configured to determine an output level of the transmission signal to be transmitted to the external device on the basis of the measured noise level, and an output execution unit configured to output a transmission signal of the determined output level to the external device.