A millimeter-wave antenna array element includes a ground layer, a first dielectric layer, a first radiation patch, a second dielectric layer, and a second radiation patch. At least a part of the first feeding part is disposed inside the first dielectric layer, or inside the second dielectric layer, or between the first dielectric layer and the second dielectric layer, and the first feeding part is insulated from the first radiation patch, the second radiation patch, and the ground layer. At least a part of the second feeding part is disposed inside the first dielectric layer, or inside the second dielectric layer, or between the first dielectric layer and the second dielectric layer, and the second feeding part is insulated from the first feeding part, the first radiation patch, the second radiation patch, and the ground layer.