Biofuel cells (BFCs) using graphene-coated carbon fiber cloth electrodes and glucose gel fuel were fabricated and evaluated. A new structure using fuel gel, in which the anode was embedded in gel and the cathode was exposed to the atmosphere, was adopted. Air-exposed biofuel cells using gel have already been reported, however, adhesion between the anode and the gel was improved by the proposed structure. In addition, the enlargement of the gel area prevented its drying. These innovations improved the power density and lifetime of the BFCs. The anode was modified with a glucose oxidase (GOD) enzyme and a mediator (ferrocene) and the cathode was modified with a bilirubin oxidase enzyme. The power density of the proposed structure was 176.4 μW/cm2 at 0.19 V, which was approximately 3.8 times higher than that of BFCs using liquid fuel (45.9 μW/cm2).