A manufacturing method of a package on package with a cavity. The method can include forming a first upper substrate cavity in one side of an upper substrate; mounting an upper semiconductor chip on the other side of the upper substrate; forming a lower substrate cavity in one side of a lower substrate; mounting a lower semiconductor chip in the lower substrate cavity formed in the lower substrate; and stacking the upper substrate above the lower substrate such that the first upper substrate cavity accommodates a part of the lower semiconductor chip. The package on package and a manufacturing method thereof can reduce the overall thickness of the package by forming cavities in both upper and lower substrates to accommodate a semiconductor chip mounted in the lower substrate.