A wiring substrate includes a base insulating film, a first interconnection formed on a top surface side of the base insulating film, a via conductor provided in a via hole formed in the base insulating film, and a second interconnection provided on a bottom surface side of the base insulating film, the second interconnection being connected to the first interconnection via the via conductor. The wiring substrate includes divided-substrate-unit regions, in each of which the first interconnection, the via conductor, and the second interconnection are formed. The wiring substrate includes a warpage-controlling pattern on the base insulating film, and has a warped shape such that when the wiring substrate is left at rest on a horizontal plate, at least a central part of each side of a plane surface of the substrate contacts the horizontal plate, with both ends of the side raised, where each of the sides extends along a second direction perpendicular to a first direction in the plane surface of the substrate.