This study investigated the factors affecting competence, focusing on mental health and work environment in care workers. Participants were 220 care workers (159 female, 61 male, mean age = 41.6 years, SD= 11.1).The mean General Health Questionnaire(GHQ) score was 5.7 (SD= 3.0), which exceeded the cut-off point.We analyzed the association among work environment,mental health， and competence using a path analysis with multiple group structural equation modeling. The fitness indicators of the models were as follows: x² /df =1.1, CFl=.999, RMSEA = .02, andAIC= 76.3. Thus, competence was affected by the GHQ and participant which is sub-factor of work environment through GHQ. In females, participant had a direct effect on the sub-factor of competence. In conclusion,improved mental health is important to promote competence in both males and females,an d improved work environment is important to promote competence in females.