This study examined the relations of educational level and life-style behaviors to the obesity. A total of 507 male adults aged 30 - 50 years completed the self-reported questionnaires. Educational level was used for measuring socioeconomic status. Activity at work, leisure-time activity and TV watching were measured for life-style behaviors related to physical activity, and some demographic and family history of disease as well. Subjects were categorized as obese when BMI was equal to or over 25kg/$m^2$, in which 19.7％ resulted obesity. Using multivariate logistic regression, the association between the measured factors and obesity was assessed. The odds ratios (OR) for risk of obesity did not differ with either age or monthly income. Subjects who completed high school (OR = 0.36; 95％ CI = 0.20 - 0.66) or university (OR = 0.34; 95％ CI = 0.16 - 0.71) had lower risk of obesity than those with education below middle school. Those with moderate activity level at work (OR = 0.41; 95％ CI = 0.24 - 0.72) showed lower risk of obesity than in inactive ones. The subjects watching TV more than 3.5 hr/day presented higher risk of obesity (OR = 2.46; 95％ CI = 1.28 - 4.74), compared with those watching TV less than 1.5 hr/day. The higher risk of obesity observed in high level of leisure time activity than in low one was considered due to that physical activity at work and leisure-time might counteract each other. Educational level and activity at work or leisure-time activity or TV watching were jointed and categorized, and then OR for obesity was estimated. The extent of obesity risk at a given level of each work activity or leisure-time activity or TV watching was different depending the educational level, which was significantly high when educational level was below middle school. Educational difference had no effect on activity level at work. However, higher educational attainment increased the leisure activity and reduced TV watching (p＜0.05), indicating that low education tended to contribute to more sedentary life-style. The findings of this study is concluded that low education was related to obesity in adult males, and its relation can partly be explained through acquiring inactive life-style behaviors. Individuals with low education might be more susceptible to the risk factors of obesity.