Provided is a package structure including a substrate, N dies, N first pads, N vertical wires, and a second pad. The N dies are stacked alternatively on the substrate, so as to form a multi-die stack structure. The N dies include, from bottom to top, first to Nth dies, wherein N is an integer greater than 1. The first die is a bottom die, and the Nth die is a top die. The first pads are disposed on an active surface of the dies respectively. The vertical wires are disposed on the first pads respectively. The second pad is disposed on the top die.