An antenna device includes: a plurality of antenna elements for a plurality of communication systems; a housing that houses the plurality of antenna elements; and a digital signal processing circuit connected to one of the plurality of antenna elements and configured to perform a demodulation process to demodulate an analog signal received by the one of the plurality of antenna elements to obtain a digital signal, or/and a modulation process to modulate a digital signal to an analog signal and output the modulated analog signal to the one of the plurality of antenna elements. At least one of the plurality of antenna elements communicates with outside of the antenna device by an analog signal on a signal line connected to the at least one of the plurality of antenna elements.