A carbon fiber-reinforced hydraulic composite material having excellent mechanical strength, workability, and freezing-and-thawing resistance, wherein chopped carbon fibers having a monofilament tensile strength of from 140 kg/mm.sup.2 to 270 kg/mm.sup.2, and a monofilament diameter of from 15 .mu.m to 30 .mu.m are blended as the carbon fibers at a ratio of from 1% to 4% by volume with respect to the entire composite material to bring a flow index of the composite material before its hardening to 120 mm or above.