To reinforce and protect a concrete structural body against tension and compression by forming a fiber reinforced thermosetting resin composite material into an external form suited to the external shape of the concrete structural body, and sticking and fittedly joining it to the concrete structural body.

A carbon fiber reinforced resin sheet 2 which is previously formed and has a spiral shape and a carbon fiber reinforced resin sheet 3 which is formed to an axial shape and has a semicylindrical shape are stuck to a concrete support 1 using a liquid adhesive agent 4 for reinforcing it. In this process, the sticking of the carbon fiber reinforced resin sheet 2 having a spiral shape may be carried out after the liquid adhesive agent 4 is hardened in a state where the carbon fiber reinforced sheet 3 having a semicylindrical shape is stuck or instantly without hardening. In addition, the number of lamination of the fiber reinforced resin sheet can be varied corresponding to a withstand load required for the concrete support 1, for example a bending load, an axial load and a deflection load which are given to the concrete support 1.