Capillary electrophoresis has been used as a new powerful tool to investigate colloidal dispersions as well as small solutes. In this letter, we report its application for observing the membrane rigidity of lipid bilayers. Multilamellar liposomes were analyzed for the purpose. When the bilayers were softened by incorporating cholesterol or short chain lipids, the migration times increased. In an experiment to observe the dependence on temperature, the viscosity-migration time relationship showed a discontinuity point near the phase transition temperature, which could be elucidated in terms of the change in the membrane rigidity due to the gel/liquid crystal transition. It is likely that the membrane rigidity significantly affects the electrophoretic mobility of liposome particles.