It is important to clarify how the breastfeeding method affects women's mental health, and how women's mental health affects the breastfeeding method in the early postpartum period when major depression and other psychiatric problems are most likely to occur. This study aimed to examine this bidirectional relationship in the early postpartum period. Participants were 2020 postpartum women who completed the Hospital Anxiety and Depression Scale (HADS) and Mother-to-Infant Bonding Scale (MIBS). We obtained data for participants' breastfeeding method for four weeks after childbirth. We performed a path analysis with factors including breastfeeding method (exclusive breastfeeding or non-exclusive breastfeeding), parity (primipara or multipara), the two HADS subscales (anxiety and depression), and the two MIBS subscales (lack of affection and anger and rejection). The path analysis showed that breastfeeding method did not significantly affect depression, anxiety, and maternal-infant bonding in the early postpartum period. Women with higher anxiety tended to use both formula-feeding and breastfeeding. Our study suggests that exclusive breastfeeding is not associated with maternal-fetal bonding in early postpartum, considering depression, anxiety, and parity.