To easily manufacture a lightweight, high strength and high rigidity FRP structure at a low cost by arranging a netlike body on the surface of a core and arranging an FRP layer including a reinforcing fiber base on the netlike body and molding them integrally.

A netlike body 7 is arranged around a core 2 and a reinforcing fiber base 8 is arranged across the entire periphery of the body 7 and further these constituents are arranged on a mold face 9, the entirety is covered with a bag film 10. In addition, the core 2 has a groove as a passageway for resin during molding is engraved over the entire periphery in the width direction of the center part. Further a resin injection port 12 is opened at a position opposite to the groove of the core 2 and a vacuum suction aperture 13 is opened at both end parts inside the bag film 10. After covering the entirely with the bag film 10, the interior of the bag film 10 is vacuumized and the resin 16 is injected through the injection aperture 12. The resin 12 thus injected is distributed along the groove inside the bag film 10 to be diffused onto the inner face of the reinforcing fiber base 8 through the netlike body 7.