An antenna device includes a circuit board and an antenna coil that includes a flexible board on which plural coil conductors are formed and a magnetic core inserted into through holes provided in the flexible board. In each of the plural coil conductors, a first conductor portion is adjacent to a first principal surface of the magnetic core and a second conductor portion is adjacent to a second principal surface of the magnetic core and are positioned so as not to overlap each other in a normal direction with respect to the first or second principal surfaces. The second conductor portion is located farther from the center of the circuit board than the first conductor portion.