To prevent back earth from flowing out by unitedly mutually connecting an upper and a lower lateral sheet pile with a plurality of steel bars to remove a gap between the upper and the lower lateral sheet pile.

A lateral sheet pile 6 is inserted between master piles 5, 5 formed of precast concrete together with processing of front earth. Anchors 9 are deeply buriedly provided in back earth 4 on a plurality of stages, and a fixed part 9a is solidly fixed with fixing nuts 9a on the side of the front earth 2 of the master pile 5. In addition, through holes 5a where the anchors are inserted through are formed at fixed intervals in the master pile 5. Abutting parts between the upper and the lower lateral sheet pile 6, 6 are further mutually connected through couplers 8. Thus the upper and the lower lateral sheet pile 6 are mutually unitedly connected with a steel bar 7.