A simple method was developed that uses microbubbles generated in liquid phase as templates to fabricate hollow microcapsules ranging 1 to several 100 µm in diameter covered with a polymer shell. In this method, we adapted a polymerization reaction or a solvent evaporation method that is a phase separation method commonly used to fabricate microspheres including core liquid. Because the microcapsules can be covered with a biodegradable polymer, they are expected to be used as ultrasonic contrast agents in medical applications.