Abstract: A carbon fiber prepreg comprising a unit layer consisting of carbon fibers and a matrix resin layer, and stranded filaments or single filaments incorporated thereinto. The steel fiber is an Ni plated low-carbon dual-phase steel filament and has a filament diameter of not more than 100 .mu.m, a tensile strength of 300 to 700 kgf/mm.sup.2, and an area reduction at fracture of more than 20%. The carbon fibers and steel filaments are aligned codirectionally, and the steel fiber content of the prepreg relative to the carbon fiber is not more than 10 vol %. Sheets of the carbon fiber prepreg are laminated to form a carbon fiber reinforced composite.