The tuning of light scattering strength has been demonstrated for organic-inorganic hybrid monoliths with well-defined through-pores in micrometer range. Macroporous gels having interconnected pores and skeletons are obtained in a system containing methyltrimethoxysilane, water, nitric acid, and methanol using an alkoxy-derived sol-gel method combined with the phase separation. The sizes of pores and skeletons can be controlled by varying molar ratios of water and methanol in the starting compositions which mostly affect the onset of polymerization-induced phase separation in the system. The mercury porosimetry shows that the resultant gels have a sharp pore size distribution, and the average pore diameter increases with increasing the amount of water and methanol. The coherent backscattering measured for the gels formed in between two slide glasses reveals that the transport mean free path of light decreases with decreasing the sizes of pores and skeletons. Pore size dependence of the scattering strength can be qualitatively explained by a Mie scattering calculation using a model in which spherical pores are randomly distributed in methylsiloxane matrix. The results indicate that the scattering strength can be tuned by controlling the sizes of the pores.