To provide a circularly polarized antenna device capable of performing axial ratio adjustment without exerting influence on a result of antenna impedance adjustment.

A circularly polarized antenna device 100 includes a tip open type loop antenna shaped parasitic radiation element 1 of which one end is a ground point 3 and the other end is an open end 4, and a feed element 2 of which one end is arranged on the ground point 3 side and the other end is arranged on the opposite side of the ground point 3 and which includes a coupling conductor 2a formed in parallel with the parasitic radiation element 1 through a clearance. The feed element 2 also includes a feeding conductor 2b of which one end is connected to a predetermined position of the coupling conductor 2a, and a feeding point 5 located on the other end of the feeding conductor 2b.