The present invention provides a thermally expandable microcapsule that is excellent in heat resistance and durability. 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 methacrylic monomer and an amide group-containing methacrylic monomer, the monomer B being at least one selected from the group consisting of a carboxyl group-containing methacrylic monomer and an ester group-containing methacrylic monomer, a total amount of the monomer A and the monomer B accounting for 70% by weight or more of the monomer mixture, a weight ratio of the monomer A and the monomer B being 5:5 to 9:1, and the monomer mixture containing methacrylonitrile and methacrylic acid in a total amount of not more than 70% by weight of the monomer mixture.