Abstract: A high speed method for formant extraction includes the steps of calculating linear prediction coefficients by executing linear prediction analysis of an input speech signal, extracting a coarse formant frequency by making a linear combination of multiple regression coefficients obtained through multiple regression analysis executed with speech feature parameters taken as predictor variables and with formant frequencies taken as criterion variables and speech feature parameters, and solving a root of an inverse filter formed of the linear prediction coefficients by an approximation method in which the coarse formant frequency is set up as an initial value of the root of the inverse filter and an approximation of root is recursively calculated until it converges to the root.