To effectively prevent a high-strength concrete member from exploding in case of a fire.

An alkaline soluble rod type resin fiber 10 is buried in an area within a predetermined depth from the concrete 1 surface, and inside the concrete 1, a plurality of rod type thin holes 4 are arranged at predetermined intervals from the surface to the depth part when the fiber is fused. Alternatively, loop type long fibers are buried, and when they are fused, a plurality of continuous linear thin holes are formed. In this way, the concrete structural body constructed by using the high-strength concrete can be effectively prevented from exploding in case of a fire.