This 3-year prospective, randomized, control, longitudinal study is aimed to (1) examine the effect of stair stepping exercise training on cardiopulmonary fitness and sleep situation in patients with Obstructive Sleep Apnea Syndrome (OSAS), and (2) follow the longitudinal change after stair stepping exercise training in patients with OSAS. Patients meet the following criteria will be invited to participate in this study: being diagnosed with AHI (Apnea-hypopnea index)＞15/hr and ODI (oxygen desaturation index)＞10/hr by Polysomnography, aged 19 or older. Based on the power analysis, 70 patients with OSAS treated in the outpatient department of Chang Gung Medical Center will be recruited over a period of 26 months. Each patient will participate in this study for seventeen weeks. Patients will be randomly assigned to receive stair stepping exercise in addition to nursing education and standard care, or nursing education and standard care alone. Stair stepping exercise will be performed at home daily for eight weeks. Outcomes will be determined by changes in the scores of cardiopulmonary fitness index, VO2max, six-minute walking distance, daytime sleepiness measured by Epworth Sleepiness Scale, sleep time measured by Actigraphy, and AHI measured by Polysomnography; those taken four times: before treatment (baseline), five weeks, nine weeks, and seventeen weeks of the study. Data will be analyzed using descriptive statistics and Generalized Estimating Equation (GEE).