This study explored how the core problems (e.g., parenting, economy, and education level) of single-parent women affect their mental health. Although parenting guilt, economic well-being, and level of education are important variables that affect the mental health of single parents, there is no study that examines the interaction effect between them together. Therefore, this study examined the moderating effects of economic well-being and level of education on the relationship between parenting guilt and mental health in 419 single-parent women. In addition, it was verified whether there was a multiple additive modulation effect when they were put in at the same time. As a result, the higher the parenting guilt and the lower the economic well-being, the higher the level of mental health pain, but the level of education had no statistical significance. However, the interaction term between parenting guilt and education level had statistical significance, while the interaction term between parenting guilt and economic well-being did not produce significant results. These findings suggest the importance of education for single-parent women’s mental health as well as the need to establish policies that allow them to have sufficient time and room for child rearing.