A manufacturing method of a semiconductor package includes the following steps. At least one lower semiconductor device is provided. A plurality of conductive pillars are formed on the at least one lower semiconductor device. A dummy die is disposed on a side of the at least one lower semiconductor device. An upper semiconductor device is disposed on the at least one lower semiconductor device and the dummy die, wherein the upper semiconductor device reveals a portion of the at least one lower semiconductor device where the plurality of conductive pillars are disposed. The at least one lower semiconductor device, the dummy die, the upper semiconductor device, and the plurality of conductive pillars are encapsulated in an encapsulating material. A redistribution structure is formed over the upper semiconductor device and the plurality of conductive pillars.