This study was undertaken to examine the degree of quality of life and to analyze the factors affecting those quality of life in middle-aged men. Method: The subjects of this study were 208 men aged by 35-55 from 3 business enterprises located in Seoul and Incheon. Data collection was conducted through the use of 5 questionnaire. Result: There were significant differences in the quality of life according to marital status, religion, educational level, number of children and total house income. A positive correlation was found between quality of life and all independent variables i.e., health promoting behaviors, health perception, social support, self-esteem and self-efficacy. Stepwise Multiple Regression Analysis revealed that the most powerful predictor was self-esteem. Self- esteem, health perception, health promoting behaviors, marriage, and social support accounted for 65% of the variance in quality of life in middle-aged men. Conclusion: All independent variables i.e., health promoting behaviors, health perception, social support, self-esteem and self-efficacy were related with quality of life in middle-aged men. Therefore it is necessary to develop the nursing intervention with these variables to increase the quality of life for middle-aged men.