Much research has been conducted in educational robotics, a new instructional technology, for K-12 education. However, there are arguments on the effect of robotics and limited empirical evidence to investigate the impact of robotics in science learning. Also most robotics studies were carried in an informal educational setting. This study examined a 10-week robotics enhanced inquiry based learning(REIBL) in formal science curriculum through an experimental research in South Korea with regard to motivation and academic achievement. The experimental group learned through REIBL approach in the science class, while the control group was taught using traditional methods. An analysis of covariance was conducted to compare the between-group differences in motivation toward science and academic achievement before and after the experiment; an interview was also conducted for the experimental group. The study results showed a significant improvement (p < 0.05) in both motivation and academic achievement in the experimental group compared with the control group. There was also positive perception about robotics as inquiry learning tool. This study will play an important role in research on the educational use of robotics in formal science education in the future.