A fuel cell is provided having excellent performance and being capable of achieving a sufficient buffer ability in a high-output operation when an enzyme is immobilized on at least one of a positive electrode and a negative electrode and of sufficiently exhibiting the ability inherent in the enzyme. A biofuel cell includes a structure in which a positive electrode and a negative electrode are opposed to each other with an electrolyte layer containing a buffer material provided therebetween, an enzyme being immobilized on at least one of the positive electrode and the negative electrode. The electrolyte layer contains as the buffer material a compound including an imidazole ring. As the compound including an imidazole ring, imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, or the like is used.