This study aims to examine a positive impact of Servant leadership(SL) for employees on their organizational citizenship behaviors (OCB), and moderating effect of job characteristics (JC) on relationship between SL and OCB. To test the hypotheses proposed, data were obtained from a sample of service workers who deal with the customers in person from 6 companies in Seoul and Gyeonggi-do. As a result of the survey, 294 out of 400 questionnaires were returned. Total 248 cases out of 294 were used for the analysis while 46 questionnaires were excluded as insufficient data. First, the results showed that servant leadership(altruistic calling, emotional healing, persuasion, wisdom, organizational stewardship) affects OCB positively. Second, this study tried to find out not only the impact of SL on OCB but also the moderating effect of the JC on the relationship between SL and OCB. About the skill variety of JC, it turned out that a group with higher JC and higher skill variety were more influential on the relationship between SL and OCB than a group with lower JC and lower skill variety. But contrary to the hypothesis, a group with low task significance and low task identity had more positive impact on the relationship between SL and OCB than a group with high task significance and high task identity. This result implies that SL’s wisdom plays an important role in causing the group with low task significance and low task identity to perform OCB conscientiously, and that SL's wisdom is not essential for the group with high task significance and high task identity. That is, not only SL but also JC plays an important role to induce employees to perform OCB. This study discussed what these research results suggest.