To provide flexibility for design of an outer surface shape of a case for an antenna apparatus.

An antenna apparatus 1 includes: a supporting base 3; a drum 10 which is rotatably supported on the supporting base 3 and has an outer circumferential surface formed in a polygonal pillar surface; an upper case 16 which covers the supporting base 3 and the drum 10 and has a groove 23 formed along a circumferential direction of the drum 10; an antenna rod 24 which extends from the outer circumferential surface of the drum 10 vertically to an axial center of the drum 10 and extends through the groove 23 to the outside of the upper case 16; and a polygonal surface 22 provided inside the upper case 16 and fitted with the outer circumferential surface of the drum 10.