A package structure including an interposer, at least one semiconductor die and an insulating encapsulation is provided. The interposer includes a semiconductor substrate and an interconnect structure disposed on the semiconductor substrate, the interconnect structure includes interlayer dielectric films and interconnect wirings embedded in the interlayer dielectric films, the semiconductor substrate includes a first portion and a second portion disposed on the first portion, the first interconnect structure is disposed on the second portion, and a first maximum lateral dimension of the first portion is greater than a second maximum lateral dimension of the second portion. The at least one semiconductor die is disposed over and electrically connected to the interconnect structure. The insulating encapsulation is disposed on the first portion, wherein the insulating encapsulation laterally encapsulates the least one semiconductor die and the second portion.