Background: : Effective communication between doctors and patients is very important not only for diagnosis and treatment but also for building trust. Although teaching communication skills is very important in medical schools, there are limitations such as the number of students and the uncertainty of the patient population. Therefore, this study evaluates the effect of Fishbowl method to teach communication skills to medical students, which involves the medical students communicating with standardized patients in front of a large classroom and being observed by rest of the students. Methods: : This study involves 10 weeks of educating 126 fourth grade medical students and graduates. During this period, total 8 classes were taken by subjects, where each class lasts 2 hours and is conducted by observing treatments of the standardized patients on 14 clinical topics by randomly selected medical students and giving feedback on the communication skills of the selected medical students. The educational effect was evaluated based on the scores of the clinical performance examination before and after the classes. Results: : The scores assessed for medical history taking before and after the training are increased by 2.45 (p<0.001) and the scores for patient-doctor relationship is increased by 7.56 (p<0.001). Conclusions : It is expected to improve the communication skills of medical students by large scale lectures with standardized patients.