An antenna device comprising: a feed element of an antenna including a first portion and a second portion having a width larger than a width of the first portion; and a non-feed element including a plurality of folded back portions (121 to 127, 171 to 177) folded back at a plurality of positions, wherein the width of the second portion of the feed element is larger than a width of the non-feed element in directions orthogonal to extensional directions of the plurality of folded back portions, at least the second portion of the feed element and the plurality of folded back portions of the non-feed element are arranged to be separated by a distance allowing the feed element and the non-feed element to be coupled to each other, the feed element is formed to extend linearly, an upper end of the second portion is open and a lower end of the first portion includes a feeding point; the non-feed element including a plurality of straight portions (121, 122, 123) formed to extend in the extensional direction of the feed element and a plurality of coupling portions (124, 125) formed to fold back the plurality of straight portions at a plurality of positions, the plurality of straight portions are coupled by the coupling portions to be folded back, and the upper end of the second portion of the feed element is arranged at substantially the same height as an upper end of a first coupling portion of the plurality of coupling portions in a plan view, and a lower end of the second portion of the feed element is arranged at substantially the same height as a lower end of a second coupling portion of the plurality of coupling portions in the plan view. a feed element of an antenna including a first portion and a second portion having a width larger than a width of the first portion; and a non-feed element including a plurality of folded back portions (121 to 127, 171 to 177) folded back at a plurality of positions, wherein the width of the second portion of the feed element is larger than a width of the non-feed element in directions orthogonal to extensional directions of the plurality of folded back portions, at least the second portion of the feed element and the plurality of folded back portions of the non-feed element are arranged to be separated by a distance allowing the feed element and the non-feed element to be coupled to each other, the feed element is formed to extend linearly, an upper end of the second portion is open and a lower end of the first portion includes a feeding point; the non-feed element including a plurality of straight portions (121, 122, 123) formed to extend in the extensional direction of the feed element and a plurality of coupling portions (124, 125) formed to fold back the plurality of straight portions at a plurality of positions, the plurality of straight portions are coupled by the coupling portions to be folded back, and the upper end of the second portion of the feed element is arranged at substantially the same height as an upper end of a first coupling portion of the plurality of coupling portions in a plan view, and a lower end of the second portion of the feed element is arranged at substantially the same height as a lower end of a second coupling portion of the plurality of coupling portions in the plan view.