A method for fabricating a package structure is provided, including the steps of: disposing on a carrier a semiconductor chip having an active surface facing the carrier; forming a patterned resist layer on the carrier; forming on the carrier an encapsulant exposing an inactive surface of the semiconductor chip and a surface of the patterned resist layer; and removing the carrier to obtain a package structure. Thereafter, redistribution layers can be formed on the opposite sides of the package structure, and a plurality of through holes can be formed in the patterned resist layer by drilling, thus allowing a plurality of conductive through holes to be formed in the through holes for electrically connecting the redistribution layers on the opposite sides of the package structure. Therefore, the invention overcomes the conventional drawback of surface roughness of the through holes caused by direct drilling the encapsulant having filler particles.