An integrated fan-out (InFO) package includes a first redistribution structure, a plurality of dies, a plurality of first conductive structures, an encapsulant, a second redistribution structure, and insulating layer, a plurality of second conductive structures, an antenna confinement structure, and a slot antenna. The dies and the first conductive structures are disposed on the first redistribution structure. The first conductive structures surround the dies. The encapsulant encapsulates the dies and the first conductive structures. The second redistribution structure is disposed on the dies, the first conductive structures, and the encapsulant. The insulating layer is over the second redistribution structure. The second conductive structures and the antenna confinement structure are embedded in the insulating layer. The slot antenna is disposed on the insulating layer.