Many students possess low confidence toward learning mathematics, which, in turn, may lead them to give up pursuing more mathematics knowledge. Recently, game-based learning (GBL) is regarded as a potential means in improving students' confidence. Thus, this study tried to promote students' confidence toward mathematics by using GBL. In addition, this study also investigated whether GBL is beneficial to all students with various abilities. The results demonstrated that this approach yielded better outcomes than the paper-based setting in both students' confidence and students' performance. The students with high and low levels of ability in the GBL group gained a significant improvement on the confidence toward mathematics. Additionally, low-ability students in the GBL group attained better mathematics performance than those in the paper-based setting.