The purpose of this study was to examine the relationship between stress urinary incontinence and pelvic floor muscle function in women using an extracorporeal biofeedback device for training. The maximal contractile power and duration of pelvic floor muscle contraction were evaluated in 147 women using this device with their clothes on. In addition, the symptoms of urinary incontinence, body composition and demographic data were investigated. A multiple logistic regression analysis was used to calculate odds ratio of individual parameters for stress urinary incontinence. As a result, childbirth experience(odds ratio:2.694, 95% confidence interval:1.058-6.859)and the duration of pelvic floor muscle contraction(0.861, 0.777-0.954)have been extracted as significant parameters. Our results suggested that slow twitch muscle fibers of pelvic floor muscle, which might contribute the duration of contraction, played an important role to prevent stress urinary incontinence.