To provide a technical means constructing a civil-engineering structure breaking no ecosystem of a natural world in the civil-engineering structure such as a subgrade and the block of the civil-engineering structure.

The block in a mininum unit constructing the civil-engineering structure has three axial beams 2 in the mutually orthogonal directions and three trussed beams 3 connecting the mutual front ends of the axial beams, and the end sections of each beam 2, 3 are connected integrally and each side of a tetrahedron as a whole is formed. A rectangular parallelopiped-shaped unit block 10 is formed by connecting and fixing the four element blocks by annexing the mutual trussed beams 3. The civil-engineering structure is built by works, in which the unit blocks 10 are hung up by a heavy machine and stacked on a foundation and the adjacent axial beams are coupled mutually. The execution of works can be conducted quickly, and the civil-engineering structure having high reliability can be constructed in a short period. A beast and a small animal can come and go through the spaces 4 of the unit blocks.