The present invention provides a thermally expandable microcapsule that is excellent in heat resistance and durability and exhibits an excellent foaming property in a wide temperature range from low temperatures to high temperatures. The present invention is a thermally expandable microcapsule, which comprises a shell containing a copolymer, and a volatile liquid as a core agent included in the shell, the copolymer being obtainable by polymerization of a monomer mixture containing a monomer A and a monomer B, the monomer A being at least one selected from the group consisting of a nitrile group-containing acrylic monomer and an amide group-containing acrylic monomer, the monomer B being at least one selected from the group consisting of a carboxyl group-containing acrylic monomer and an ester group-containing acrylic monomer, a total amount of the monomer A and the monomer B accounting for 70% by weight or more of the monomer mixture, and a weight ratio of the monomer A and the monomer B being 5:5 to 9:1.