1. A method of manufacturing a wiring substrate, comprising:forming a resist in which an opening portion is provided, on a supporting plate;
forming a concave portion in the supporting plate through the opening portion of the resist;
forming a metal layer for a connection pad in the concave portion of the supporting plate and the opening portion of the resist, by an electroplating utilizing the supporting plate as a plating power feeding path;
removing the resist;
after removing the resist,
forming a ring-like part of the supporting plate around an outer periphery part of the metal layer as a convex level difference portion whose height is higher than other etched surfaces, by etching the supporting plate while using the metal layer as a mask;
forming an insulating layer covering the metal layer, on the supporting plate; and
exposing the metal layer by removing the supporting plate.