An antenna device with an attachment member includes an antenna including a radiation plate provided with radiation face that radiates vertically polarized waves, a housing portion that houses the antenna, an attachment member that attaches the housing portion to a vehicle, and a metal fixing portion that is formed in an elongated shape to one end of the attachment member, that abuts a back face of the housing portion facing toward an opposite side to the radiation face, and that fixes the housing portion. Viewed from a thickness direction of the radiation plate, the fixing portion is disposed between a first region formed to the back face on one side in the extension direction of a first straight line, and a second region formed to the back face on another side in the extension direction of the first straight line.