This experiment was conducted to explore the effect of emotional face feedback on task performance. Ten participants were asked to perform an operant learning task in which they were to learn contingencies between key-pressing and consequences (gain or loss) for each of several target patterns, and to maximize their total score. For performance feedback stimuli, we used three types of facial expressions (Angry, Happy, Neutral), and two types of symbol conditions (〇[correct], ×[error]). In NA condition, a neutral face was presented as correct feedback and an angry face was presented as error feedback. In the HN condition, a happy face was presented as correct feedback and a neutral face was presented as error feedback. In the NN condition, different neutral faces were presented as correct and error feedback. In the 〇× condition, 〇 was presented as correct feedback and × was presented as error feedback. We also reversed the conditions (AN, NH, ×〇), in order to examine whether the congruency of feedback valence (e.g. correct-positive and error-negative) was critical. Results indicated that lower error rates were observed in the angry face feedback condition (NA and AN) as compared to the happy face condition (p<.05). We also found a congruency effect between the behavioral results and feedback valence in response time of subsequent trials. These findings suggest that emotional face feedback might be related to task performance during an operant learning task.