An antenna device (1, 1a-1c) characterized in comprising: a plurality of antenna elements (50, 50a-50f) respectively configured to receive incident waves coming from an object and output a first received signal on a basis of received incident waves, the plurality of antenna elements including at least a first antenna element that receives incident waves of a predetermined polarization direction and a second antenna element that receives incident waves of a polarization direction different from the incident waves received by the first antenna element; a plurality of modulating units (60, 60a-60f) respectively configured to modulate the first received signal output from each of the antenna elements into a second received signal, such that the second received signal has a frequency corresponding to a position of the antenna element in the antenna device and has a phase corresponding to the polarization direction of the incident waves received by the antenna element, so that the plurality of second received signals have a plurality of different frequencies corresponding to the respective positions of the antenna elements in the antenna device and have phases corresponding to the polarization directions of the incident waves received by the antenna elements; a synthesizing unit configured to synthesize the plurality of second received signals respectively modulated by the plurality of modulating units so as to generate one synthetic signal; a signal processing unit (100, 110, 70, 80) configured to perform predetermined signal processing on the synthetic signal; and an extracting unit (120, 120a-120e, 140a-140e) comprising band-pass filters configured to extract third received signals from the synthetic signal on which has been performed the predetermined signal processing, each of the third received signals having a frequency and a phase equal to the frequency and the phase of the second received signal modulated by the modulating unit. a plurality of antenna elements (50, 50a-50f) respectively configured to receive incident waves coming from an object and output a first received signal on a basis of received incident waves, the plurality of antenna elements including at least a first antenna element that receives incident waves of a predetermined polarization direction and a second antenna element that receives incident waves of a polarization direction different from the incident waves received by the first antenna element; a plurality of modulating units (60, 60a-60f) respectively configured to modulate the first received signal output from each of the antenna elements into a second received signal, such that the second received signal has a frequency corresponding to a position of the antenna element in the antenna device and has a phase corresponding to the polarization direction of the incident waves received by the antenna element, so that the plurality of second received signals have a plurality of different frequencies corresponding to the respective positions of the antenna elements in the antenna device and have phases corresponding to the polarization directions of the incident waves received by the antenna elements; a synthesizing unit configured to synthesize the plurality of second received signals respectively modulated by the plurality of modulating units so as to generate one synthetic signal; a signal processing unit (100, 110, 70, 80) configured to perform predetermined signal processing on the synthetic signal; and an extracting unit (120, 120a-120e, 140a-140e) comprising band-pass filters configured to extract third received signals from the synthetic signal on which has been performed the predetermined signal processing, each of the third received signals having a frequency and a phase equal to the frequency and the phase of the second received signal modulated by the modulating unit.