To provide a construction method of a plate-like preceeding shore strut capable of accurately controlling an injection amount of grout of cement milk without moving earth and sand containing cement having some fear of causing the pollution of the environment and forming the plate-like preceeding shore strut by a soil cement hardening body having stabilized property.

A plate-like preceeding shore strut is so constituted that the ratio of water to cement of cement milk and a grouting required amount are calculated in advance, the ground having the capacity equivalent to the grouting required amount of cement milk is waterlessly excavated in the shape of a trench by an excavator such as back-hoe, shovel or the like to move excavated earth, then, the lower ground of an excavated section is excavated by chain saw type trenching machine 7 or the like, cement milk and earth and sand are mixed while injecting cement milk into the trench from the front end of the trenching machine and that the injection of cement milk is stopped at a point of time when the surface of mixture is raised up to the neighborhood of the ground surface.