An antenna device includes an antenna element 10 and a printed circuit board 20 on which the antenna element 10 is mounted. The antenna element 10 includes a base 11 which is made of a dielectric material and a radiation conductor formed on at least one surface of the base 11. The printed circuit board 20 includes ground clearance region 23a having substantially a rectangular shape and having one side contacting an edge of the printed circuit board and other three sides surrounded by an edge line of a ground pattern, an antenna mounting region 27 provided within the ground clearance region 23a, and at least one frequency adjusting element 30 provided within the ground clearance region 27. The frequency adjusting element 30 is provided on the far side of the antenna mounting region 27 as viewed from an edge 20e of the printed circuit board 20.