The purpose of this study was to empirically yield item characteristics of three sub-dimensions of organizational commitment scale. Recent studies relevant to organizational commitment have claimed that organizational commitment, perse, contained three sub-dimensions that had been explored in various academic fields. Of such studies, Allen and Meyer (1990) reorganized controversies and developed three-dimensional organizational commitment scale composed of affective, continuance, and normative dimensions, which afterwards has been used frequently in North America, indicating whose high reliability and validity verified empirically. However, past research has not revealed characteristics of items which compose of each subscale neither in North America nor in Japan. In the present study, questionnaire survey was conducted using 292 Japanese workers as respondents and the data were analyzed primarily by exploratory factor analysis to investigate dimensionality, followed by Item Response Theory (IRT) techniques to yield item and test (dimensional) characteristics. Results showed that:(1) dimensional classification was revealed as valid;(2) both attitudinal commitment and normative commitment dimensions were reliable enough; and (3) each item and dimension was well-structured and useful for discriminating and being sensitive for respondents with various levels of latent trait theta. Implications for future research were discussed.