A communication device includes: an electromagnetic-wave generating unit for outputting an electromagnetic wave; and a transmitting/receiving unit for transmitting data by modulating the electromagnetic wave in accordance with data and receiving data transmitted from the other device by demodulating the electromagnetic wave outputted by the electromagnetic-wave generating unit or the electromagnetic wave outputted by the other device as the other party of communication, wherein the transmitting/receiving unit transmits attribute information indicating communication ability of the device and receives attribute information indicating communication ability of the other device, and the electromagnetic-wave generating unit reduces power of the electromagnetic wave to be outputted after receiving the attribute information.