To provide a technology for suppressing emission of stronger radio wave due to a mismatched combination of a communication device with an external antenna module. A communication device comprises: a connector that is connected to an external antenna module; a generating section that generates a transmitting signal of a specific frequency band, the transmitting signal being supplied to the antenna module via the connector; an acquiring section that acquires information relating to antenna gain from the antenna module; and a controlling section that executes predetermined processing on the basis of the information relating to antenna gain, such that strength of radio wave emitted from the antenna module responsive to the transmitting signal does not exceed an upper limit value defined for the specific frequency band.