PROBLEM TO BE SOLVED: To provide a natural ground reinforcing method for forepiling work, face reinforcing work, etc., which reinforces the front natural ground when e.g. a tunnel, an underground opening, etc. are excavated, which enhances adhesion at the weak material age of a cement-based consolidation material for anchoring a reinforcing pipe as a reinforcing material, which prevents the outflow and runway of the consolidation material even in the production of sump water, which can bring about a great anchoring force even in the fragile condition of the natural ground by increasing rigidity so as to enhance a reinforcing effect. SOLUTION: In this natural ground reinforcing method, a drilled hole (h) is formed at a predetermined angle of elevation in the natural ground 1 ahead of a cutting face from inside a tunnel excavation space T; concurrently with that, a reinforcing pipe 6, which is formed by sequentially connecting one or more pipes with an ejection hole for the consolidation material to a peripheral wall, is driven into the drilled hole (h); and an anchoring or consolidation area 8 is formed for reinforcement in the reinforcing pipe 6 and the natural ground 1 around it by injecting the consolidation material into the reinforcing pipe 6. Characteristically, a material, in which glass fibers are mixed into the cement-based consolidation material such as cement milk and cement mortar, is used as the consolidation material. COPYRIGHT: (C)2010,JPO&INPIT