To achieve an increase in the mass of an energy dissipating rope net to resist the large inertia force of rolling and falling huge rocks, and to latently prepare a large swelling margin.

A rope net 12 is mounted on a middle and high level rope 14 built across a top end vicinity lower part 13 of a pillar 1 in a substantially suspended state that it short hung inside a metal gauze 5. The rope net includes one rope vertically extending while taking a zigzag path, the other adjacent rope taking a zigzag path in a backward direction, and a weight 19 arranged in the mutual proximity part of both ropes. This weight makes it possible to form a rhombic mesh larger than the metal gauze by disposing those respective ropes at insertion parts disposed at two right and left parts, to develop a swelling capability by allowing the deformation of the mesh, and to contribute to an increase in the mass of the rope net 12.