Introduction: Maternal stress is harmful to the placenta. It induces apoptosis. Maternal folic acid (FA) supplementation is mandatory in Indonesia and other countries. FA is known as an antioxidant and probably reduces the apoptosis index in placenta with maternal stress. Aim: To investigate the folic acid supplementation in pregnant stress mice (Mus Musculus) on the apoptosis index and placental TNFα expression. Methods: Twenty-one Mus musculus strainded balb/c female mice were randomly divided into three groups. The first group was normal mice, the second group was given stress, and the third group was given stress and folic acid supplementation (3 mg/kg body weight/day in 0,5ml suspension). The ovulation was induced by pregnant mare's serum gonadotropin and HCG. The stress was given by immobilizing the mice in a transparent pipe and giving bright light twice a day on gestational day 10-15. On gestational day 16, the mice were sacrificed, and the placenta tissue was taken. The expression of TNF-α and apoptotic index was calculated by multiplying the score for % stained cells and staining intensity. Result: The expression of TNF-α (mean±SD) of the normal, second, and third groups were 2.1±0.37, 5.9±1.01, and 3.2±1.78. The apoptotic index (mean±SD) of the normal, second, and third groups were 2.7±1.09, 6.3±0.87, and 3.2±0.65. Conclusion: Folic acid supplementation reduces TNF-α and apoptotic index expression in the placenta with maternal stress, and there is a positive correlation between TNF-α and apoptotic index.