Parkinson's disease (PD) has an average onset age of 55 years old. Its incidence increases with age. Due to an aging demographic, PD poses an increasing burden on patients and health care resources. PD causes tremors, rigidity, abnormal gait, postural instability, and freezing of gait. These symptoms diminish patients' quality of life. Continuous rehabilitation of PD patients is more effective in the long term than either pharmacotherapy or surgical treatment. Nevertheless, a patient's motivation for rehabilitation suffers from the difficulties associated with the need for frequent visits to a rehabilitation center. The purpose of this study is to develop a serious game based on augmented reality for the rehabilitation of patients with PD. The game was designed to allow patients with PD to ambulate while following virtual visual cues in a real environment as well as incorporated levels with increasing difficulty. We assess improvements in gait and a sense of balance after 3 weeks of training. The results show that all patients have had improvements in these two outcomes. The results of this study provide references for future study and develop more or methods of playing rehabilitation games.