The purpose of this study was to measure the organizational commitment of sports volunteer and to obtain some ideas for organization management. The questionnaire used for the study was designed for, and the data collected from, 242 volunteers participating in the Special Olympics Nippon. These volunteers provide sports programs in Japanese communities for individuals with mental retardation. Fifteen organizational commitment statements were measured using a 5-point Lickert-type scale. The means were computed for each statement and the means of the 15 statements were then computed. The data were compared by personal characteristics, statuses of involvement and soon. The main results were as follows : (1) The overall mean score for the 15 organizational commitment statements was 3.72, indicating that the level of organizational commitment of the sample was not particularly low. The subjects felt that they gained many benefits through their volunteer activity. However, they were not active in the organization's activities. (2) There were no remarkable differences in organizational commitment except for differences related to the amount of spending money. However, closer examination of the results from analysis of the 15 organizational commitment statements revealed subtle differences in volunteer commitment to the organization. (3) Organizational commitment shows some differences related to continuation of the activity, the amount of payment for the activity, and whether or not individuals have posts in the organization.