To substantially reduce deflection and bending moment to external force of a penetration blade at the front end of a hollow pile in the rotary penetration holloy pile with a nose blade, to substantially decrease stress concentration in the jointing section of the penetration blade and the hollow pile and to lower the resistance of a ground, in the rotary penetration.

The sectional shape of a penetration blade, having a spiral shape or the like installed at the nose of the hollow pile 1 rotational-penetrated into a ground, is formed into a downwards or upwards curved curved-plate shape or a downward or upward inclined plate shape, the downward curved-plate shape penetrating blade 2, the downward inclined-plate shaped penetration blade 3 or the like are mounted at the nose of the hollow pile, and deflection and bending moment to external force of the penetration blade are reduced significantly. Stress concentration in the jointing section of the penetration blade and the hollow pile is decreased significantly, and large resistance is obtained even when the wall thickness of the penetration blade and the hollow pile is thinned. The plan-view shape of an excavation edge 6 at the lower end of the penetration blade is formed into a curved shape, and the resistance of the ground is lowered.