In this study we aimed to examine the contents of humor in the Japanese workplace and to understand the effects of humor on mental/physical health and self-evaluation of job performance. Japanese workers (N = 436) responded to questionnaires addressing workplace humor, feelings about workplace, workplace communication, mental/physical health, and perceived job performance. An exploratory factor analysis indicated that there are five types of workplace humor: norm-violating humor, experience-sharing humor, workplace-enjoying humor, people-recalling humor, and outside-mocking humor. A covariance structural analysis showed that norm-violating humor and workplace-enjoying humor decreased mental and physical health by promoting both negative feelings in the workplace and self-disclosure about the negative side of work. Results also revealed that experience-sharing humor, people-recalling humor, and outside-mocking humor had a positive effect on the self-evaluation of job performance as well as mental and physical health, by promoting both positive feelings and mutual communication in the workplace. Results suggest that humor in the workplace has various influences on workers depending on the type of workplace humor.