An antenna device includes: a line-shaped antenna conductor with a predetermined length; an actuator member that directly supports the line-shaped antenna or supports the line-shaped antenna via an auxiliary member and is displaceable integrally with the antenna conductor, where the actuator member is displaced to change a position of the antenna conductor in a space; and an attaching member that attaches the actuator member and the antenna member in one longitudinal end of the antenna conductor to a communication apparatus. The actuator member performs displacement control in which one longitudinal end of the antenna conductor serves as a fixed support and the other end thereof serves as a free end to be displaceable depending on the control voltage.