A manufacturing method of a microchemical chip made of a resin and having a micro channel, which comprises forming a photoresist film over the surface of one side of a metal support substratum, stacking a photomask for the formation of a channel pattern over the photoresist film, forming a minute-structure photoresist pattern over the metal support substratum by a photofabrication technology as a flat-sheet mold, disposing the flat-sheet mold or unit mold obtained by separating the flat-sheet mold on the bottom of a contour forming frame for resin molding, pouring a resin into the contour forming frame for resin molding and curing the resin to form a resin structure having a micro channel formed by the mold, and attaching the resin structure having a micro channel to a flat sheet to be a lid of the micro channel; and microchemical chips manufactured by this method.