Purpose: This study was done to evaluate the efficacy of Nei-Guan acupressure on nausea and vomiting in patients undergoing laparoscopic prostatectomy with intravenous patient controlled analgesia (IV-PCA). Methods: Data were collected between August 13, 2012 and January 31, 2013 at a hospital in Busan. The participants were 45 men, who underwent the surgery laparoscopic prostatectomy, with IV-PCA. Data were analyzed using descriptive statistics, $x^2$-test, repeated measures ANCOVA and Games-Howell test with PASW 18.0. Results: Nei-Guan acupressure had an interaction effect on nausea between group and time (F=5.01, p<.001), group (F=10.80, p<.001), time (F=26.51, p<.001) in laparoscopic prostatectomy with IV-PCA and also an interaction effect on vomiting between group and time (F=2.77, p=.032), group (F=8.89, p=.001), time (F=4.01, p=.022). Conclusion: Results indicate that nei-guan acupressure is a potentially effective therapy for the prevention of nausea and vomiting which occur with IV-PCA. Therefore, if patients complain of nausea and vomiting when receiving IV-PCA, nurses can provide patients with information about nei-guan acupressure and help them with nausea and vomiting.