1. A method of normalizing a speech feature vector, the method comprising: dividing a variable section of the speech feature vector into a predetermined number of sections; calculating a probability distribution function corresponding to each of the divided sections; and normalizing a histogram for the speech feature vector, using a backward cumulative distribution function which cumulates the probability distribution function in an order from a greatest to a smallest value, so that a statistical feature of the speech feature vector is similar to a model vector.