Reinforcement is an important environmental variable that increases the motivation for the work of people with intellectual disabilities. Variables affecting the effect of reinforcement are type of reinforcement, schedule of reinforcement, and immediacy of reinforcement. In recent years, “distribution of reinforcement”, which is a combination of reinforcement schedule and immediate reinforcement, has been newly proposed(DeLeon, Chase, Frank-Crawford, Carreau-Webster, Triggs, Bullock, & Jennet, 2014; Frank-Crawford et al., 2018; Hoffman, 2017). Providing a small amount of reinforcement immediately after each reaction is called distributed reinforcement. It is called accumulated reinforcement that provides a cumulative amount of reinforcement after repeated positive reactions, and it is said that the effect of each type of reinforcement is different for each individual. However, although the effect of distribution of reinforcement is influenced by the difficulty of the task(Joachim & Carroll, 2017; Kocher et al., 2015; Ward-Horner et al., 2017a), there is no research that simultaneously manipulated the distribution of reinforcement and the difficulty of the task. Therefore, the purpose of this study was to investigate the effect of the arrangement of reinforcement of children and adolescents with intellectual disabilities by manipulating the distribution of reinforcement and task difficulty: 1. Immediate reinforcement in easy tasks, 2. Cumulative reinforcement in easy tasks, 3. Immediate reinforcement in difficult tasks, and 4. Cumulative reinforcement in difficult tasks.