Formaldehyde (FA) is an important irritant compound in pesticide to induce asthma and allergy in respiratory system. Alveolar macrophage is also an pivotal cell in the immune response of respiratory system. However, the effect of FA in macrophage cell viability has not been elucidated. Thus, this study was conducted to investigate the effect of FA on apoptosis in Raw 264.7 cells, alveolar macrophage cell line. In this study, FA decreased cell viability of lung alveolar macrophage cells in a dose-dependent manner (>$100{mu}M$). FA-induced decrease of cell viability was blocked by the treatment of antioxidants (vitamin C, NAC, and catalase). Indeed, FA induced lipid peroxide formation in Raw 264.7 cells. FA decreased Bcl-2 expression but increased Bax expression in lung alveloar macrophage cells. In addition, FA also increased the cleaved form of caspase-3. In conclusion, FA induced apoptosis via oxidative stress in cultured Raw 264.7 cells.