Internet gaming disorder (IGD) is a neurodevelopmental disorder characterized by dysfunctional reward processing. Recent studies combined experimental techniques of cognitive neuroscience to explore the neural mechanisms of IGD, and the existing results seem to indicate that the neural basis underlying IGD resembles those of drug addiction. However, the conclusions of the current research are still controversial. The differences were not surprising for two main reasons. One is that there is evidence of specificity to reward processing of different types, which means gaming addicts assign higher incentive value to gaming-related cues than other rewards. The appeal of game is that instant and unexpected rewards give the player a thrill that is hard to experience in reality. Besides, the stage of reward processing is another important factor. The game player can learn the game skill according to the feedback of practice again and again and achieve the upper level, in this way, reward processing can be decomposed into two phases: reward anticipation and outcome evaluation. Reward anticipation refers to the emotional and motivational states triggered by reward-related cues, while outcome evaluation refers to the hedonic experience when rewards are obtained. Thus, this review has compared different types of rewards and discussed different stages of reward processing among IGD patients based on the existing researches. We found the hyperactive reward system of IGD patients in reward anticipation may be associated with attention bias, emotional experience, and craving. In contrast, IGD patients show blunt activity to primary reward, especially the outcome evaluation. In order to conduct a more comprehensive and in-depth study on reward processing in IGD, further studies are required to eliminate comorbid subjects, use gaming rewards with higher ecological validity, and explore how the impairment of outcome evaluation contributes to the development of addictive behaviors.