A spatial distribution of diffuse reflectance produced by obliquely incident light is not centered about the point of light entry. The value of shift in the center of diffuse reflectance is directly related to the absorption coefficient \mu_{a} and the effective attenuation coefficient \mu_{eff}. \mu_{a} and the reduced scattering coefficient \mu^{'}_{s} of human skin tissues in vivo are measured by oblique-incidence reflectometry based on the two-source diffuse theory model. For ten Chinese volunteers aged 15-63 years, \mu_{a} and \mu^{'}_{s} are noninvasively determined to be 0.029-0.075 and 0.52-0.97 mm^{-1}, respectively.