The absorption coefficient and reduced scattering coefficient of tofu were determined at 633 nm by spatially resolved diffuse reflectance at different soymilk coagulation temperatures. Added absorber method, in which ink is added to a sub-sample, was used to determine the two optical coefficients separately. The two coefficients were compared with viscosity. The reduced scattering coefficient increased with coagulation temperature, while the absorption coefficient showed no significant change. Since the order of the absorption coefficient was much smaller than that of the reduced scattering coefficient, scattering was more dominant than absorption in tofu. Also since the correlation between the reduced scattering coefficient and viscosity was observed, it can be used to evaluate the quality of tofu.