Purpose: The purpose of this study was to investigate the sexual function of male patients receiving rectal cancer and to analyze the factors related to sexual function. Methods: This study included 71 male patients undergoing outpatient treatment after surgery at C University Hospital, Chonnam, Korea from April 1 to September 1, 2014. The sexual function of males with colorectal cancer was calculated using the Korean Translation of International Index of Erectile Function(IIEF). Data analysis was performed using t-test, ANOVA, and regression analysis. The study was IRB approved. Results: The sexual function index scores of the subjects were 33.28±19.47 points. Regression analysis showed that sexual function increased as the duration after operation increased(p=.001), higher location of cancer(p=.007), age decreased(p=.013). The explanatory power (adj. R2) of the analysis model was 0.186. Conclusion: Sexual function of males with rectal cancer differed according to duration after operation, and location of cancer, age. Therefore, medical staff think that it can be used as basic data for appropriate education and counseling by age, time, and type of treatment to improve sexual function of men with rectal cancer.