Electro-conductive fibers comprise synthetic fibers and an electro-conductive layer containing carbon nanotubes and covering a surface of the synthetic fibers, and the coverage of the electro-conductive layer relative to the whole surface of the synthetic fibers is not less than 60% (particularly not less than 90%). The electric resistance value of the electro-conductive fibers ranges from 1×10−2 to 1×1010 Ω/cm, and the standard deviation of the logarithm of the electric resistance value is less than 1.0. The thickness of the electro-conductive layer ranges from 0.1 to 5 μm, and the ratio of the carbon nanotubes may be 0.1 to 50 parts by mass relative to 100 parts by mass of the synthetic fibers. The electro-conductive layer may further contain a binder. The electro-conductive fibers may be produced by immersing the synthetic fibers in a dispersion with vibrating the synthetic fibers to form the electro-conductive layer adhered to the surface of the synthetic fibers. The electro-conductive fibers have the carbon nanotubes homogeneously and firmly adhered to an almost whole of a surface thereof and have an electro-conductivity and a softness.