To provide a protective material of a waterproofing layer capable of having no fear to impair the waterproofing layer or the like when a structure moves and having high workability and safety in the case of carrying out construction work.

The protective material 1 of the waterproofing layer is so constructed that the protective material 1 of the waterproofing layer is installed for the waterproof layer 4 provided across two structures in an underground connection section of the structure 2 and the structure 3. The protective material 1 is formed by adhesively fixing two buffer sections 1b constituted of an elastic body to a protective plate 1a. The protective material 1 is fixed to the structure 2 and the structure 3 by respectively adhering two buffers 1b to the structure 2 and the structure 3. After the protective material 1 is fixed, back filling soil 7 is repeatedly carried out by back filling and rolling around the structures 2 and 3 and the protective material 1 by a heavy machine to bury and harden it up to a predetermined height.