To provide a ground impregnation method and a ground injection pipe used for the method to a structure back face for positively injecting grout into the ground of the structure back face from the face of a structure skeleton constructed in the ground, disusing impregnation from the ground surface heretofore performed.

In this ground impregnation method and ground injection pipe to the structure back face, a soil improved part is constructed for the construction of a new structure attached to the structure skeleton in the ground. An injection hole 9 of prescribed length is bored with jet water 7 from the tip of a rod 4 while delivering the rod from the structure skeleton 1, and then grout 11 is injected from the rod to construct the soil improved part 14.