This study examined the social wellbeing of working mothers of preschool children with the aim of identifying relationships between social wellbeing and influencing factors, focusing on the individual, relationship, and work environment of the mothers. Data on 390 working mothers were used for this study. The data were analyzed using the SPSS 18.0 program and descriptive statistics. Pearson’s correlation analyses and hierarchical regression analyses were performed. The results show that social wellbeing has significantly positive correlations with education, monthly household income, number of children, age of the first child(8 and over), social capital for childcare, division of childcare, maternal role values, spouse’s beliefs about paternal parenting involvement, and family-supportive work environment, as well as significantly negative correlations with weekly working hours, sociological ambivalence, spouse’s beliefs about father’s breadwinner role and gender-role values, job overload, and gender-role attitudes of coworkers. In addition, hierarchical regression revealed that spouse’s beliefs about paternal parenting involvement and a family-supportive work environment were significantly positive predictors of working mothers’social wellbeing, whereas working mothers’sociological ambivalence toward their roles, job overload, and gender-role attitudes of coworkers were significantly negative predictors of working mothers’social wellbeing. These results point to ways of changing education and policy to improve the social wellbeing of working mothers.