To reasonably form an intermediately size of L-shaped retaining wall by applying the constitution that the reinforcement group of a ready-made wall element having an erected wall body of concrete is projected over the prescribed length from the vicinity of the lower end of a back along the prescribed direction, and buried in a footing part made of concrete placed in an excavated groove.

An wall element 3 of a concrete square plate has a part 4a of buried reinforcement group 4 projected along the prescribed direction from the vicinity of the lower end of a back 3a. Rag-stones 7 are spread on the bottom of an excavated groove 6 formed at a retaining wall construction site, and bearing steel rods 1 are arranged on the upper surface of the rag-stones 7, depending on the breadth of the wall element 3. After leveling concrete 8 hardens, the wall element 3 is positioned and jointed along prostrate preventive steel rods 2 erected on the bearing steel rods 1 for use as an erected wall part. Then, concrete 10 is placed in space between the back 3a of the wall element 3 in the excavated groove 6 and a form, thereby forming a footing part. At the same time, the part 4a of the reinforcement group 4 of the wall element 3 is buried in the concrete 10.