A wiring substrate includes a resin substrate in which first and second through holes are formed, a metallic foil on one surface of the resin substrate coating the through holes and separated into first and second side metallic foils by a border, a first connecting portion formed by a plating film inside the first through hole, a second connecting portion formed by a plating film inside the second through hole, a first slit facing the border and penetrating through the metallic foil and the first connecting portion, a second slit facing the border and penetrating through the metallic foil and the second connecting portion, first and second plating layers on front surfaces of the first and second side metallic foils, bottom surfaces of the first and second connecting portions, and side surfaces inside the first and second slits of the first and second side metallic foils.