This study analyzes how the fertility effects of pro-natal policies, such as cash and child care supports, differed by income group. For the purpose, we estimated and used the county-level total fertility rate by employment status and income, based on the Korean National Health Insurance data for the entire population. The results suggest that the effects of pro-natal policies differed by socioeconomic group. In general, cash and child care supports had stronger positive effects on fertility of middle- and higher-income households than the rest. This result perhaps indicates that richer families are at the “margin” of having children. This study provides the following implications. First, it will be desirable to evaluate the effectiveness of a policy by observing changes experienced by individuals at the margin, not based on its average effect. Second, it would be effective to mix various pro-natal policies that are supplements to one another. Finally, it is necessary to consider potential heterogeneity among different socioeconomic groups in preparing policy measures and selecting indices for evaluation.