To enhance the shear reinforcement effect of a reinforced concrete structure by distributing a tension resulting from cracking produced in a concrete and preventing a shear reinforcement member from being loosened off.

The shear reinforcement member 12 bent in U-shape which includes a first leg part 12a, a second leg part 12b, and a connection part 12c for connecting the first leg part 12a and the second leg part 12b is disposed on the reinforcement surface 24a of the side wall 24 of a box culvert 20 which is an existing reinforced concrete structure so as to straddle two main reinforcements 26a, 26b and to be positioned in proximity to the main reinforcements 26a, 26b. Since the tension resulting from the cracking is shared by the first and second leg parts 12a, 12b, and the shear reinforcement member 12 is hooked on the main reinforcements 26a, 26b, the shear reinforcement member 12 is prevented from being loosened off.