A method for producing a polyether-polyol having a narrow molecular weight distribution, which comprises carrying out selective fractional extraction of the low-molecular weight component from a polyether-polyol (A) having an average molecular weight of from 500 to 4500 represented by formula (1): HO—[(CH2)4O]n—[(CR1R2)pO]q—H  (1) wherein R1 and R2, which may be the same or different, each represents a hydrogen atom or a linear or branched alkyl group having from 1 to 5 carbon atoms; n indicates a positive integer; p indicates an integer of from 1 to 8; and q indicates 0 or a positive integer, by the use of an aqueous solution (C) containing from 15 to 70 wt % sulfuric acid at a room temperature to 100° C., to thereby suitably determine the amount of the aqueous sulfuric acid solution to the overall organic layer and the sulfuric acid concentration in accordance with the molecular weight and molecular weight distribution of the intended polyether-polyol to be fractionally extracted.