An antenna device including: a substrate; a plurality of antenna elements supported by the substrate, each of the antenna elements having a feeding point; and a parasitic element supported by the substrate and having no feeding point, in which the plurality of antenna elements is disposed to be spaced apart from each other along a predetermined direction, the parasitic element is mutually spaced apart in the direction from a first antenna element located on an end side in the direction among the plurality of antenna elements, and a first element interval between the parasitic element and the first antenna element is equal to or less than twice a second element interval between the first antenna element and a second antenna element located on an opposite side of the parasitic element with respect to the first antenna element.