Purpose: The purpose of this study was to examine late-onset hypogonadism, erectile dysfunction, depression, and quality of life among middle-aged male workers. Methods: The subjects included 343 men aged between 40 and 64, responded to self-report questionnaires on general characteristics, late-onset hypogonadism, erectile dysfunction, depression, and quality of life. Data were collected from May 16, 2012 to October 9, 2012 and analyzed using t-test, ANOVA, $x^2$-test, hierarchical multiple regression. Result: The prevalence rate of late-onset hypogonadism was 63.8% with high points in reduction of libido, energy, physical strength and endurance, and erectile function. There were significant differences in late-onset hypogonadism according to age($x^2$=8.98, p=.048) and in erectile dysfunction according to age(F=11.03, p<.001), monthly income(F=2.84, p=.024) and smoking( t=2.96, p=.018). Significant differences were also found in depression according to educational level(F=8.12, p<.001) and in quality of life according to monthly income(F=7.21, p<.001). The factors which influenced quality of life were late-onset hypogonadism, erectile dysfunction, depression, marital status and religion. Conclusion: Symptoms of erectile dysfunction can be improved by smoking cessation education program. In order to improve the life quality of middle-aged men, nursing intervention programs that would both provide proper knowledge on climacteric syndrome and alleviate symptoms should be designed while, at the same time, other programs to evaluate, prevent and control depression are developed.