The purpose of this study is to examine the effect of vocation instruction using peer supervision and feedback of adults with intellectual disabilities on beauty assistance task skill of peer adults with intellectual disabilities. For this, three individuals with intellectual disabilities recommended as trainees preparing for vocational life with a workplace related to group home at a welfare center were selected as subjects. Also, peer supervision and feedback were used as the main principles of instruction as a part of peer tutoring so that subjects can participate in instruction within the context of their group home and living culture. Peer supervision and feedback were specifically applied under the context of instruction with the use of smart pad and linguistic facilitation. In addition, subjects used peer supervision and feedback through intervention procedure of types 1 and 2, which combine positions as learners and teachers. Beauty assistance task skill as a dependent variable was operationally defined as a skill of shampooing hair of customers in the wash room of beauty salon. As a result of this study, subjects were found to effectively acquire and maintain hair beauty assistance task skill through vocation instruction using peer supervision and feedback of adults with intellectual disabilities.