NOVELTY - The upper surface (3) of a core material (2) is processed into the shape of to-be-molded product. Steps (5a,5b) are formed in the side (4) of core material (2) facing another core material (2). A composite material is cured on the surface of core material to form a composite material layer (8). A tapered portion (10) is formed on layer (8) to obtain structural components (1a,1b), which are then bonded. A composite material is laminated to the tapered portion, heat source (16) is arranged, covered, and polished to obtain a composite-material molding die.    USE - Manufacture of composite-material molding die (claimed) used for manufacturing aircraft components and windmill components.    ADVANTAGE - The method is capable of producing composite-material molding die regardless of the size of an autoclave.    DETAILED DESCRIPTION - The upper surface of a core material is processed into a shape corresponding to the shape of a to-be-molded product. Steps are formed in the side of core material facing another core material, when two core materials are arranged side by side. A non-hardened composite material is laminated on the surface of core material and cured by heat-pressurizing, to form a composite material layer. A tapered portion having a thickness gradually reduced towards the side surface is formed on the composite material layer located on another surface, which is perpendicular to the surface of side of the core material, to obtain structural components. An adhesive agent (12) is applied to the side and the structural components are bonded. A non-hardened composite material is laminated to the tapered portion and a heat source is arranged with respect to the composite material. The composite material and heat source are covered with a packaging material, and the composite material is hardened by evacuating the packaging material and heating by the heat source. The surface of bonded structural component is polished, to obtain a composite-material molding die. An INDEPENDENT CLAIM is included for composite-material molding die.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view explaining the manufacturing method of composite-material molding die. (Drawing includes non-English language text)    Structural components (1a,1b)    Core material (2)    Upper surface (3)    Side (4)    Steps (5a,5b)    Composite material layer (8)    Tapered portion (10)    Adhesive agent (12)    Heat source (16)