An antenna device is provided. The antenna device includes a first substrate and a second substrate facing the first substrate. The first substrate includes an inner surface and an outer surface opposite the inner surface of the first substrate. The second substrate includes an inner surface and an outer surface opposite the inner surface of the second substrate. The antenna device also includes a die disposed between the first substrate and the second substrate, a redistribution layer disposed between the die and the inner surface of the second substrate, and an antenna unit electrically connected to the die via the redistribution layer. The antenna unit is arranged on at least one of the inner surface of the first substrate, the outer surface of the first substrate, the inner surface of the second substrate, and the outer surface of the second substrate.