The quantitative measurement of phonation time is the needful procedure in the diagnosis of any vocal disorders. Each subject was told to take a deep breath and make a vowel sound with constant pitch and intensity as long as he could. It is the purpose of this study to acknowledge how much the expiratory movement during the phonation is converted into a single vowel sound efficiently with 40 subjects. The author has made a brief literature review and has obtained the following results ; 1) The average normal phonation time in male was 30.2 seconds and 21.6 seconds in female. It would be proper to consider pathological if the phonation time is shorter than 15 seconds in male and shorter than 10 seconds in female. 2) There was no significant differences in phonation time between standing and sitting position. 3) The phonation time was shortened in loud voice. 4) There would be no significance in the phonation time if its differences were within 10 seconds of normal limit in the same person. 5) It is best to choose the maximal value among 3 consecutive measurements.