An antenna device includes an antenna, the antenna including an antenna element, a circuit board, and a planar metallic holder disposed between the antenna element and the circuit board. The antenna device further includes an antenna case accommodating the antenna, and the antenna case include a top cover and a bottom plate serving as a base. The metallic holder supports the antenna element on the base, and includes a flat-shaped portion mounting a bottom surface of the antenna element and a plurality of tabs extending upwards from peripheral edges of the flat-shaped portion. The plurality of tabs includes a pair of front tabs and a pair of rear tabs, and a distance between the pair of front tabs is shorter than a distance between the pair of rear tabs.