The purpose of this study is developing a virtual bicycle system for improving the ability of postural balance control for adults in various age groups. The system consists of an exercise bicycle that allows tilt in accordance with the postural balance of the subject in the system, a visual display that shows virtual road, and a visual feedback system. The rider of the system tries to maintain balance on the bicycle with a visual feedback of a virtual road while the pedaling speed, the heading direction, and various weight distribution information are updated to the subject as visual feedbacks in the display. A series of experiments were performed with various subjects to find the factors related to postural balance control in the system. The related parameters obtained were weight shift, magnitude of the deviation from the center of the virtual road, and variables related to the movement of the center of pressure. The results found that the ability to control postural balance in the system improved with the presentation of visual feedback information of the distribution of weight. It was also found that the general performance of the subject on balance in the system improved after ten days long training. The results show that the newly developed system can be used for the diagnosis of postural balance as well as for the stimulation of various senses such as vision and somatic sense in the field of rehabilitation training.