An object of the present invention is to suppress occurrence of disturbance in pass amplitude characteristics within a band and disturbance in return loss characteristics in the band due to total reflection, improve cutoff performance, and acquire a favorable gain. An antenna device 1 includes a waveguide body 5 including a coaxial waveguide conversion unit 6 that includes an inner space 8 and a connector attachment hole 22, and a closure member 30. The antenna device 1 also includes a connector 50 including a connector body 51, a center conductor 60, and a radiator 54 b configured by an end portion 60 a of the center conductor that adapts the protruding length of the end portion to a specific frequency band.