PURPOSE: To obtain a structure having a high regidity, by a method wherein upper and lower flange members (consisting of a synthetic resin and reinforcing fibers), web members, corner members and a pressure bag are sealed in a rigid metallic mold having a desired shape, and molding is conducted under heating while pressurizing the bag, wherein the corner members are triangular in shape.

CONSTITUTION: An outside skin material 82 is placed on a lower metallic mold 80. The material 82 is a synthetic resin sheet containing reinforcing fibers. An uncured main girder member 84 consisting of a fiber-reinforced resin and the flange members consisting of a honeycomb material 86 are placed on the material 82, and further an outside skin material 88 is placed thereon. The triangular corner members 40 are placed on the main girder member 84, and further the web members 42 are placed thereon. Then, the pressure bag 44 is inserted between the web members 42. An upper mold 46 is placed on the lower mold 80 and is closed. Molding is conducted by heating the molds 80, 46 while exerting a pressure on the bag 44. Then, the mold is released to obtain a wing.