Package structure and method of forming the same

A package structure is provided, including: a first redistribution structure including a first dielectric layer and a first redistribution circuit disposed in the first dielectric layer; a second redistribution structure including a first portion and a second portion, wherein the first portion disposes on the first redistribution structure and electrically connects to the first redistribution structure, and the second portion disposes on the first portion and electrically connects to the first portion; wherein a circuit density of the second portion is lower than that of the first portion; wherein the first portion includes a second dielectric layer and a second redistribution circuit disposed in the second dielectric layer; the second portion includes a third dielectric layer, a third redistribution circuit disposed in the third dielectric layer, and a stiffener layer disposed in the third dielectric layer, wherein the stiffener layer is separated from the third redistribution circuit by the third dielectric