The purpose of this study was to investigate the effect of personality traits of the middle aged on quality of life while mediated by self-concepts such as self-efficacy and self-derogation, as well as while moderated by subjective socio-economic variables such as economic status, social activities and employment. To verify the conceptual causality model and moderating effects of contextual variables, we analysed 353 cases out of purposively collected 400 cases from a medium sized city. As results, first, conscientiousness of personality traits positively affected quality of life of the middle aged while mediated by self-concepts. Second, neuroticism of personality traits negatively affected quality of life while mediated by self-concepts. Third, agreeableness of personality traits did not eventually affect quality of life, although affected negatively on self-efficacy and positively on self-derogation. Fourth, socio-economic variables such as economic status, social activities and employment moderated various paths in the model, which indicated dynamics of internal variables were affected by contextual variables.