The present invention provides a thermoplastic microcapsule which is softened by heat, has a good thermoexpandability, and can provide a MICROBALLOON which shows a high heat resistance after thermoexpanded; such a thermoexpandable microcapsule is composed of a shell and an expanding agent therein, in which said shell is made from a copolymer essentially consisting of a polymerizable monomer having two or more polymerizable double bonds and a monomer which can produce a homopolymer having a high glass transition temperature, and said expanding agent is vaporizable at a temperature lower than the softening temperature of the copolymer.