One of the popular training methods to improve sport performance is medicine ball (MB) training. MB training can increase the speed of trunk rotation or the stability of the trunk. Theoretically, both of those changes in a kinetic chain of the body can cause a positive effect on golf swing mechanics; however the effect of the training on golf performance is still unclear. Thus, the purpose of this study was to clarify the effects of 8 weeks of MB training on golf performance for skilled golfers.