A signal transmission system evaluation apparatus acquires statistics about a variation in a characteristic value and a limit value of the characteristic value corresponding to a given range of variation, with respect to each of the characteristic values which represent characteristics of the components. The apparatus calculates a probability distribution with respect to each of the characteristic values, based on the statistic acquired, calculates an eye-opening of the signal transmission system in case that the characteristic value is the limit value, makes an adjustment of the limit value. The apparatus calculates a yield rate of the signal transmission system based on the probability distribution and the limit value.