PURPOSE: To reinforce bearing capacity of soil, prevent differential settlement, and to improve drainage so as to stabilize and strengthen ground by using a concrete block for roadbed that is composed of an angular roadbed, a polygonal body, and of an axial leg provided in the lower center thereof.

CONSTITUTION: For a concrete block (b), a cylindrical or polygonal axial leg 6 whose angle of tip shoe is defined as 90° to 120° is provided in the lower center of a body 5 in which the tilt angle of the oblique line of an angular roadbed 4 is 45°, and the axial leg part 6 and the body part 5 are integrated together through a reinforcing bar. On a polygonal line and/or corner of the polygon on the upper surface of the block (b), one or more notch 7 is formed. Into a groove hole 2 for which a crust 1 is excavated, a filler 3 composed of a waste plastic, etc., is put and is pressure-filled up, while on the upper layer of the filler 3, blocks (b) are placed closely, which is pressure-filled up and buried while bound with sand, so as to form a buffer layer body (a) that is tightly strengthened, and to homogeneously lay a roadbed surface.