A heat-resistant bilirubin oxidase mutant is disclosed. The bilirubin oxidase mutant is obtained by deletion, replacement, addition or insertion of at least one amino acid residue of a wild type amino sequence of SEQ. ID. No. 1 of a bilirubin oxidase derived from an imperfect filamentous fungus, Myrothecium verrucaria. A biocathode including a thermo stable bilirubin oxidase mutant immobilized thereon, and its use in a biofuel cell is disclosed.