To provide a small-sized antenna device and an azimuth detecting device capable of changing a beam direction two-dimensionally.

A transmitting side supplies electric power via a Rotoman lens 41 to a transmitting antenna section 10 comprised of a plurality of unit antennas AU arranged along a first scanning direction, thereby performing one-dimensional scanning along the first scanning direction. A receiving side performs one-dimensional azimuth detection along a second scanning direction based on a receiving signal (beat signal) obtained for each unit antenna AU from a receiving antenna section 20 comprised of a plurality of unit antennas AU arranged along the second scanning direction. Two-dimensional azimuth detection is performed by combining of the foregoing. A longitudinal width (an angle range along the first scanning direction) of a receiving beam is set to be broader than the scanning scope of a transmitting beam, and a vertical width (an angle range along the second scanning direction) of the transmitting beam is set to be broader than the scanning scope of the receiving beam.

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