A method of molding composite materials to be joined to a skin having a panel shape inclined at a first inclination angle with respect to an XZ plane from a Z-axis in a Y-direction in a three-dimensional orthogonal coordinate system, the method comprising: a shaping process of shaping a laminate having fiber sheets laminated over one another, by bending the laminate in an X-direction and the Y-direction such that a cross sectional shape of the laminate becomes the same along a Z-direction; and a molding process of: mounting the laminate that has been shaped, onto a mold material having a change in shape from the Z-axis in the Y-direction; impregnating a resin material into the laminate while adjusting an amount of the resin material filled therein; and molding the composite materials that have cured into a shape having a first inclined surface (11;21) inclined at the first inclination angle with respect to the XZ plane from the Z-axis in the Y-direction, such that the composite materials that have cured have a shape complementary to the panel shape of the skin, wherein the mold material has a first inclination molding surface that molds the first inclined surface (11;21) and serves as a joint surface to the skin, and a second inclination molding surface that molds a surface of the composite materials, the surface being opposite to the first inclined surface (11;21), into a second inclined surface (12;22) having a second inclination angle smaller than the first inclination angle. a shaping process of shaping a laminate having fiber sheets laminated over one another, by bending the laminate in an X-direction and the Y-direction such that a cross sectional shape of the laminate becomes the same along a Z-direction; and a molding process of: mounting the laminate that has been shaped, onto a mold material having a change in shape from the Z-axis in the Y-direction; impregnating a resin material into the laminate while adjusting an amount of the resin material filled therein; and molding the composite materials that have cured into a shape having a first inclined surface (11;21) inclined at the first inclination angle with respect to the XZ plane from the Z-axis in the Y-direction, such that the composite materials that have cured have a shape complementary to the panel shape of the skin, wherein the mold material has a first inclination molding surface that molds the first inclined surface (11;21) and serves as a joint surface to the skin, and a second inclination molding surface that molds a surface of the composite materials, the surface being opposite to the first inclined surface (11;21), into a second inclined surface (12;22) having a second inclination angle smaller than the first inclination angle. mounting the laminate that has been shaped, onto a mold material having a change in shape from the Z-axis in the Y-direction; impregnating a resin material into the laminate while adjusting an amount of the resin material filled therein; and molding the composite materials that have cured into a shape having a first inclined surface (11;21) inclined at the first inclination angle with respect to the XZ plane from the Z-axis in the Y-direction, such that the composite materials that have cured have a shape complementary to the panel shape of the skin, wherein the mold material has a first inclination molding surface that molds the first inclined surface (11;21) and serves as a joint surface to the skin, and a second inclination molding surface that molds a surface of the composite materials, the surface being opposite to the first inclined surface (11;21), into a second inclined surface (12;22) having a second inclination angle smaller than the first inclination angle.