A method of manufacturing a wiring substrate, includes obtaining a laminated body in which a first copper tin alloy layer and a copper layer are arranged in sequence on a first coupling agent layer, on a first insulating resin layer, forming a seed layer on the copper layer, forming a plating resist in which an opening portion is provided on the seed layer, forming a metal plating layer in the opening portion of the plating resist by applying an electroplating that utilizes the seed layer as a plating power feeding path, removing the plating resist, and forming a first wiring layer on the first coupling agent layer by etching the seed layer, the copper layer, and the first copper tin alloy layer while using the metal plating layer as a mask.