In the business ethics field, many empirical studies have been conducted with the aim of elucidating the antecedents of the concept of “unethical behavior” of employees. When evaluating unethical behavior using a questionnaire, the 16 items developed by Newstrom & Ruch(1975)are still widely used. In this paper, we categorize the Newstrom & Ruch(1975)scale into two types to examine the differences in their antecedents. We employ hierarchical multiple regression analysis with moral disengagement and organizational commitment(affective/continuous)as independent variables. The results demonstrate that moral disengagement promotes both types of unethical behavior. Furthermore, we find that affective commitment and continuance commitment each affect only different types of unethical behavior. This suggests that constructing different prevention measures for these two types of unethical behaviors is necessary.