A manufacturing method of a lead frame substrate includes: applying a photosensitive resist or a dry film to first and second surfaces of a metal plate; pattern-exposing the photosensitive resist or the dry film, and then developing the first surface and the second surface to form on the first surface a first resist pattern for forming a connection post and to form on the second surface a second resist pattern for forming a wiring pattern; etching the first surface partway down the metal plate to form the connection post; filling the first surface with a pre-molding resin to a thickness with which the etched surface is buried; removing the pre-molding resin uniformly in a thickness direction of the pre-molding resin until a bottom surface of the connection post is exposed; and etching the second surface to form a wiring pattern.