Although previous studies have reported that black soybean has chemopreventive potential, the underlying mechanisms remain unclear. Upregulation of cyclooxygenase-2 (COX-2) has been known to be a key mediator in the development of skin cancer. The present study investigated the effect of black soybean (Glycine max cv. Heugmi) seed coat extract (BSE) on 12-O-tetradecanoylphorbol-13-acetate (TPA) or ultraviolet-B-(UVB)-induced COX-2 expression, and its underlying mechanisms. The TPA- or UVB-induced COX-2 expression in mouse skin epithelial cells were dose-dependently inhibited by BSE treatment. BSE suppressed the COX-2 promoter activity. BSE also attenuated the transactivation of activator protein-1 (AP-1) and nuclear factor (NF)-${kappa}B$, transcription factors of COX-2 expression in mouse skin epithelial cells transfected stably with AP-1 and NF-${kappa}B$ luciferase promoter, respectively. Furthermore, BSE inhibited the activation of MAPKKs/MAPKs pathways that otherwise induced by TPA or UVB. Collectively, BSE suppresses TPA or UVB-induced COX-2 expression by blocking the expressions of MAPKKs/MAPKs pathways, which may contribute to its chemopreventive potential.