PURPOSE: To simplify the contruction work of an underground continuous wall by a method in which a specific connecting block is erected in a forward pit and then a specific iron bar cage is erected in the adjacent backward pit.

CONSTITUTION: Two forward pits 1 are excavated at a given interval, a connecting block 2 with connecting iron bars 4 projected from both ends of concrete blocks, for example, is erected in the pits 1, and bagged cement mortars 6 are charged to form projections, whereby preventing the creeping of concrete and the moving of the block. Then, a backward pit 8 is excavated between both the pits 1, a body 10 to reinforce the center of the wall of an oblong cross section and an iron bar cage 9 with plural connecting iron bars 11 projected from both ends of the body 10 are erected in the pit, both the iron bars 4 and 11 are connected with each other, and concrete is placed into the pit 8. By this, the need for the charging of pebbles, as in the conventional cases, can be eliminated.