The aim of this study was to investigate whether Monascus-fermented soybean extracts (MFSE) containing natural estrogen-like compounds such as isoflavones and mevinolins has potential effects on human osteoblast-like SaOS2 cells using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and alkaline phophatase (ALP) assaies. MFSE exerted biphasic dose-dependent effect; stimulating osteoblastic activity at low concentrations and inhibiting SaOS2 cells viability at high concentrations. At $10^{-8}-10^{-4};mg/mL$, MFSE is not only non-cytotoxic but also induced comparatively high ALP activity on SaOS2 cells. ALP activity (%) significantly increased (220.1%, p<0.05) when SaOS2 cells were treated with MFSE at a concentration of $10^{-5};mg/mL$, whereas slowly increased (185.6%, p<0.05) in unfermented soybean extracts (UFSE) at $10^{-3};mg/mL$. The potentially greater ALP activity of MFSE compared to the UFSE might partially be caused by its mevinolin, which was derived from the soybean during Monascus-fermentation. Our findings indicate that supplementation of MFSE may accelerate the speed of intracellular ALP synthesis by the bone cells when provided at optimal dosages.