An antenna device includes an antenna base including a plurality of first fitting parts, the plurality of first fitting parts being arranged with mutual spaces therebetween in a periphery edge part of the antenna base, an antenna case fixed to the antenna base, an antenna part arranged in a space enclosed by the antenna base and the antenna case, and a cover member including a plurality of a second fitting parts, each of the plurality of the second fitting parts fitting with each of the plurality of the first fitting parts.