Disclosed is an antenna device including element antennas for receiving signals, phase control units for controlling the phases of the signals received by the element antennas, a phase value series acquiring unit for acquiring phase value series in which phase values differing among the element antennas and changing with time are provided, a phase value setting unit for setting the phase values to the phase control units in accordance with the phase value series, a combining unit for combining the signals whose phases are controlled into a composite signal, an ADC for digitizing the composite signal, a frequency calculating unit for calculating frequency shift amounts from the phase value series, DDCs for performing frequency conversion on the digitized signal by using the frequency shift amounts, LPFs each for performing low-pass filtering on the signal on which the frequency conversion is performed, and a beam forming unit for forming one or more beam signals by using the signals on each of which the low-pass filtering is performed.