PURPOSE: To shorten a construction term by laying a panel provided with each enclosing frame for its upper and lower surfaces after subgrade course material has been laid in a dug-down constructing groove, and thereby forming a surface layer with subgrade upper course material, asphalt and the like.

CONSTITUTION: A weak ground is excavated into a road constructing groove 8, and subgrade lower material 6 land down. Over the material 6 panels 2 each of which is composed of a flat plate provided with each enclosing frame at the peripheries of its upper and lower surfaces for reinforcing the panel and preventing its side slip, are laid while being arranged in parallel side-to-side. Furthermore, a surface layer composed of subgrade upper course material 7, a stabilizing treatment layer 5, asphaltconcrete and the like is formed over the aforesaid panels. Besides, each panel 2 may be provided with partitions 2d as required, and each panel 2 may be directly laid over the bottom surface of an excavated groove. By this constitution, the construction and repair of the road over the weak ground can thereby be efficiently carried out.