Microencapsulation of glass beads was carried out by in situ polymerization with melamine and formaldehyde. Glass beads were chosen as a core material because of their narrow size distribution and spherical shape. The complicated influence of emulsion on microencapsulation was successfully excluded by the use of a solid core material with a narrow size distribution and in situ polymerization, where all reactants are supplied from outside of the cores. Glass beads were microencapsulated systematically under various experimental conditions, and the effects of dosages of initiator and dispersing agent, stirring rate, and concentration and ratio of melamine and formaldehyde on microcapsules were investigated.