The formation processes of nanostructures in spherical mesoporous silica were investigated for a two-phase system consisting of hydrophobic tetrabutoxysilane (TBOS) and an alkali solution containing a surfactant as a template. The formation process was deduced as follows: During the initial 2 hours of the reaction, the surfactant in the aqueous phase was extracted with water molecules into the TBOS phase and W/O type microemulsion were formed. Then, the hydrolysis and condensation of TBOS subsequently proceeded at the interface and/or in the water pools in microemulsion, and the viscosity in the TBOS phase increased. After 8 hours, spherical mesoporous silica dispersed in the aqueous phase was obtained under the agitation. The water pools in the TBOS phase were connected to each other, and a regularly arranged nanostructure was formed by the self-assembly of surfactant. Thus, the nanostructure of spherical mesoporous silica was determined to be the reverse of MCM41, in which the continuous mesopores were developed. The solubilizing quantity of phenol for the reversed MCM41, was greater than those for MCM41 and MCM48, due to the continuous mesopore structure.