There are provided a coating composition, for use on a plastic lens with a refractive index exceeding 1.60, for avoiding interference fringes and unevenness in the reflected color, and a lens coated with such coating composition. The coating composition contains an organic silicon compound represented by R.sup.1.sub.a R.sup.2.sub.b Si(OR.sup.3).sub.4-(a+b) and modified sol of a double structure in which nuclei composed of tin oxide colloid particles are surrounded by tin oxide-tungsten oxide complex colloid particles, and the plastic lens is coated with such coating composition.