PROBLEM TO BE SOLVED: To provide a reinforcing method capable of securing the stability of a masonry wall at a low cost.
SOLUTION: The reinforcing method is applied to the masonry wall 16 piling up a wedge stone 14 by making a backing cobble stone layer 12 intervene in the front of an inclined bedrock 10, a drilling hole 18 reaching the backing cobble stone layer 12 is formed in a joint section of the wedge stone 14, and grout 20 is injected in the backing cobble stone layer 12 through the drilling hole 18. The drilling hole 18 is formed from the front side of the masonry wall 16 by a small drilling machine. The grout 20 flows to the outside of the drilling hole 18 along a gap between cobble stones of the backing cobble stone layer 12, and after that, it is solidified after a certain time has passed. When the grout 20 is solidified, the cobble stones existing around the drilling hole 18 are connected to one another by making the grout 20 intervene to locally form an approximately bar-shaped hardening part 22.