An antenna device is provided. The antenna device includes a circuit board including a first side configured with a transmission unit, and a second side opposite to the first side; a main radiator disposed at the first side, electrically connected to the transmission unit, and having a major axis direction; a first parasitical radiator adjacent to the main radiator, and coaxially disposed in the major axis direction at the first side; and a second parasitical radiator coaxially disposed in the major axis direction at the second side.