A carbon fiber-made reinforcing woven fabric comprising a carbon-fiber woven fabric formed from warps consisting of carbon fibers and wefts consisting of carbon fibers, and auxiliary yarns arranged along at least either warps or wefts, the auxiliary yarns being passed over and under other yarns differently from associated warps or wefts. When prepreg is produced by applying matrix resin to this woven fabric by a wet/prepreg processing method before drying, the presence of auxiliary yarns in gaps in the vicinities of warp-weft intersections on the woven fabric allows matrix resin to remain around auxiliary yarns to produce no apertures in the obtained prepreg, whereby the woven fabric is suitable for a prepreg production by wet/prepreg processing.