Disclosed is a beam steering antenna structure, including two parallel metallic boards, an antenna perpendicularly disposed between the two metallic boards, a plurality of substrates perpendicularly disposed between the two metallic boards and radially disposed around the antenna, and a bias voltage circuit. Each of the substrates has a plurality of metal units cyclically aligned thereon, and each of the metal units includes two metallic regions oppositely disposed and in no contact with each other and a transistor disposed between the two metallic regions for coupling the two metallic regions. The transistors are electrically connected to the bias voltage circuit to thereby control the steering direction of beam radiation by switching the transistors.