The goal of this study is to validate the KAIST-Ewha Colonoscopy Simulation II as a training tool by examining the sectional learning curve of the trainees' performance on the simulation. Nine subjects including three fellows and six residents in the internal medicine participated in this study. All the subjects practiced the colonoscopy on the simulation until their performance surpasses the criteria preset by colonoscopy experts. Performance of the subjects during all the trials was measured in terms of eight performance indices and analyzed according to the colon segments. The results show that the trainees' skills significantly improved through training on the KAIST-Ewha Colonoscopy Simulation II. Particularly, most of the improvement appeared in the sigmoid and descending colon. On the other hand, there was little improvement in the ascending colon.