A method for manufacturing a wiring substrate having a sheet, including: (a) arranging a wiring substrate and a sheet between a board and a tool in a manner that a resin layer comes between the wiring substrate and the sheet, one surface of the wiring substrate being a concave/convex surface and the other surface being flat, and both surfaces of the sheet being flat; (b) pressing the wiring substrate, the resin layer, and the sheet using the board and the tool so as to adhere the resin layer to both the wiring substrate and the sheet, in that: the board having a flat surface is arranged in a manner that the flat surface faces the tool; the tool contains an elastic body having a projecting part projecting in a direction of the board; the resin layer is arranged so as to overlap with a concave part and a convex part of the concave/convex surface; and the pressing step (b) starts with a tip of the projecting part of the tool and the flat surface of the board and proceeds while expanding a pressing surface of the tool by widening a tip plane of the projecting part using deformation of the elastic body.