An antenna element includes a dielectric substrate, a first ground electrode, a second ground electrode, a via conductor, and a radiation electrode. The dielectric substrate includes a first portion shaped like a flat plate and a second portion thinner than the first portion. The first ground electrode is arranged in the first portion. The second ground electrode is arranged in the second portion. The via conductor couples the first ground electrode and the second ground electrode. A distance between the radiation electrode and the first ground electrode in a first thickness direction is more than a distance between the radiation electrode and the second ground electrode in a second thickness direction. Part of the radiation electrode lies opposite to the first ground electrode without lying opposite to the second ground electrode.