A package structure including an interposer, a semiconductor die, through insulator vias, an insulating encapsulant and a redistribution layer is provided. The interposer includes a core structure having a first and second surface, first metal layers disposed on the first and second surface, second metal layers disposed on the second surface over the first metal layers, and third metal layers disposed on the second surface over the second metal layers. The semiconductor die is disposed on the interposer. The through insulator vias are disposed on the interposer and electrically connected to the plurality of first metal layers. The insulating encapsulant is disposed on the interposer over the first surface and encapsulating the semiconductor die and the plurality of through insulator vias. The redistribution layer is disposed on the insulating encapsulant and electrically connected to the semiconductor die and the plurality of through insulator vias.