A mode/polarization antenna device according to an embodiment includes a plurality of unit mode/polarization antennas having a one-dimensional or two-dimensional arrangement structure, the plurality of unit mode/polarization antennas being arranged at a half-wavelength interval, each unit mode/polarization antenna among the plurality of unit mode/polarization antennas including three or more antennas, and a number of elements of a union of main modes of the antennas being greater than or equal to a number of the antennas.