A communication device of an embodiment includes a communication control unit capable of transmitting a signal based on a plurality of different communication protocols and changing a communication protocol used for communication from a first communication protocol to a second communication protocol, in which the communication control unit does not transmit a signal based on a third communication protocol until a signal based on the second communication protocol is transmitted, but transmits a signal based on the second communication protocol in which at least two of a plurality of communication elements defined by the first communication protocol are changed.