An antenna device includes a support pole, a fixing seat mounted on the support pole, at least one clamping member mounted on the support pole and combined with the fixing seat by at least one locking bolt, and an antenna box mounted on the fixing seat. The fixing seat is provided with a square mounting sleeve which has a mounting chamber and two opposite fixing holes. The antenna box has a square insertion block inserted into the mounting chamber. The insertion block has a plurality of adjusting holes. Thus, the orientation of the antenna box is adjustable so that the antenna box can be disposed at a horizontal position or a vertical position so as to receive a wireless signal exactly and clearly.