An antenna device comprising: a plurality of element antennas for receiving signals, each element antenna being provided in an individual system; a plurality of phase shifters provided for the respective systems, each phase shifter being provided to control a phase of a signal received by a corresponding one of the element antennas; a phase value series acquiring unit for acquiring phase value series in which phase values differing among the systems and changing with time are provided; a phase value setting unit for setting a phase value to each phase shifter in accordance with the phase value series acquired by the phase value series acquiring unit; a combining unit for combining signals whose phases are controlled respectively by the plurality of phase shifters to provide a composite signal; an AD converter for digitizing the composite signal provided from the combining unit; a frequency calculating unit for calculating a frequency shift amount for each system from the phase value series acquired by the phase value series acquiring unit; a plurality of frequency converting units provided for the respective systems, each frequency converting unit being provided to perform frequency conversion on the signal digitized by the AD converter by using a corresponding frequency shift amount calculated by the frequency calculating unit; a plurality of filtering units provided for the respective systems, each filtering unit being provided to perform low-pass filtering on the signal on which the frequency conversion is performed by a corresponding one of the frequency converting units; 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 by one of the filtering units. a plurality of element antennas for receiving signals, each element antenna being provided in an individual system; a plurality of phase shifters provided for the respective systems, each phase shifter being provided to control a phase of a signal received by a corresponding one of the element antennas; a phase value series acquiring unit for acquiring phase value series in which phase values differing among the systems and changing with time are provided; a phase value setting unit for setting a phase value to each phase shifter in accordance with the phase value series acquired by the phase value series acquiring unit; a combining unit for combining signals whose phases are controlled respectively by the plurality of phase shifters to provide a composite signal; an AD converter for digitizing the composite signal provided from the combining unit; a frequency calculating unit for calculating a frequency shift amount for each system from the phase value series acquired by the phase value series acquiring unit; a plurality of frequency converting units provided for the respective systems, each frequency converting unit being provided to perform frequency conversion on the signal digitized by the AD converter by using a corresponding frequency shift amount calculated by the frequency calculating unit; a plurality of filtering units provided for the respective systems, each filtering unit being provided to perform low-pass filtering on the signal on which the frequency conversion is performed by a corresponding one of the frequency converting units; 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 by one of the filtering units.