Provided are Circular Polarized Helical Radiation element and its Array Antenna operable in TX band and RX band. The circular polarized helical radiation element and its array antenna and the antenna with double reflection boards using that array can operate at TX/RX dual band which is high frequency such as Ka band by operating the helical antenna in axial mode and implementing dual feeding structure. The array antenna having a number of radiation elements operable in the both of TX band and RX band, wherein the radiation elements are arrayed on predetermined column lines, each radiation element comprising: a helix for radiating orthogonal circular polarized waves in the different frequency bands wherein the helix is fed at its beginning point and its terminating point; and a wave guide for accommodating the helix.