A package structure including a semiconductor die, an insulating encapsulant, and a redistribution layer is provided. The semiconductor die includes a semiconductor substrate, a plurality of metallization layers disposed on the semiconductor substrate, and a passivation layer disposed on the plurality of metallization layers. The passivation layer has a first opening that partially expose a topmost layer of the plurality of metallization layers. The insulating encapsulant is encapsulating the semiconductor die. The redistribution layer includes at least a first dielectric layer and a first conductive layer stacked on the first dielectric layer. The first dielectric layer has a second opening that overlaps with the first opening, and a width ratio of the second opening to the first opening is in a range of 2.3:1 to 12:1. The first conductive layer is electrically connected to the topmost layer of the plurality of metallization layers through the first and second openings.