Purpose: The purpose of this study was to identify the risk factors that influence surgical site infections after surgery. Methods: This study was a retrospective research utilizing Electronic Medical Records. Data collection targeted 4,510 adult patients who had 8 different kinds of surgery (gastric surgery, colon surgery, laparoscopic cholecystectomy, hip & knee replacement, hysterectomy, cesarean section, cardiac surgery) in 4 medical care departments, at one general hospital between January 2006 and December 2011. Multivariate logistic regression analyses were used to identify the risk factors affecting surgical site infections after surgery. Results: Risk factors for increased surgical site infection following surgery were confirmed to be age (OR=1.59, p<.001), BMI (Body Mass Index)(OR=1.25, p=.034), year of operation (OR=2.45, p<.001), length of operation (OR=3.06, p<.001), ASA (American Society of Anesthesiology) score (OR=1.36, p=.025), classification of antibiotic used (OR=2.77, p<.001), duration of the prophylactic antibiotics use (OR=1.85, p<.001), and interaction between classification of antibiotic used and duration of the prophylactic antibiotics use (OR=1.90, p=.016). Conclusions: Results suggest that risk factors affecting surgical site infections should be monitored before surgery. The results of this study should contribute to establishing effective infection management measures and implementing surveillance systems for patients who have actual risk factors.