Effects of leadership of the head nurse on organizational commitment and morale of subordinate nurses were examined, by taking leader's personality and social power as moderator variables. Some 318 nurses at two hospitals were snrveyed. An original scale was constructed in order to tap social power, and a four factor structure was identified. Factors of referent/expert (attractive) power, coercive power, legitimate power and reward power were extracted. Using this scale, it was discovered that referent/expert (attractive) power exerted moderator effects on the relationship between leadership P behavior and both commitment and morale, while legitimate power also had a moderator effect on the relationship betweem leadership M behavior and commitment. Furthermore, years of experience of nurses showed moderator effects on delegative leadership behavior and morale.