An antenna device comprising: a reflecting mirror configured to focus a received radio wave into a predetermined focusing position; a primary radiator configured to be connected with a wireless device including a transmitter and a receiver; a radiator support mechanism configured to rotatably support the primary radiator at the focusing position of the reflecting mirror with respect to a central axis of the primary radiator; a support mechanism configured to support the reflecting mirror; a tilt sensor configured to detect a polarization direction angle of the primary radiator that is a tilt angle of a polarization plane of the primary radiator or an angle of the support mechanism configured to support the reflecting mirror to the horizontal plane; evaluation data acquisition means configured to acquire tilt evaluation data indicating the polarization direction angle of the primary radiator or indicating the angle of the support mechanism configured to support the reflecting mirror to the horizontal plane, from the tilt sensor, and level evaluation data indicating a reception level that is a level of a radio wave received by the receiver using the primary radiator; polarization plane adjustment means configured to adjust the polarization plane of the primary radiator based on the tilt evaluation data and the level evaluation data; and trigger input means configured to input a trigger to the polarization plane adjustment means, wherein the polarization plane adjustment means is configured to rotate the primary radiator based on the tilt evaluation data, and then rotates the primary radiator based on the level evaluation data to adjust the polarization plane, according to timing provided by the trigger. a reflecting mirror configured to focus a received radio wave into a predetermined focusing position; a primary radiator configured to be connected with a wireless device including a transmitter and a receiver; a radiator support mechanism configured to rotatably support the primary radiator at the focusing position of the reflecting mirror with respect to a central axis of the primary radiator; a support mechanism configured to support the reflecting mirror; a tilt sensor configured to detect a polarization direction angle of the primary radiator that is a tilt angle of a polarization plane of the primary radiator or an angle of the support mechanism configured to support the reflecting mirror to the horizontal plane; evaluation data acquisition means configured to acquire tilt evaluation data indicating the polarization direction angle of the primary radiator or indicating the angle of the support mechanism configured to support the reflecting mirror to the horizontal plane, from the tilt sensor, and level evaluation data indicating a reception level that is a level of a radio wave received by the receiver using the primary radiator; polarization plane adjustment means configured to adjust the polarization plane of the primary radiator based on the tilt evaluation data and the level evaluation data; and trigger input means configured to input a trigger to the polarization plane adjustment means, wherein the polarization plane adjustment means is configured to rotate the primary radiator based on the tilt evaluation data, and then rotates the primary radiator based on the level evaluation data to adjust the polarization plane, according to timing provided by the trigger.