An electrically conductive graphene-polystyrene composite was prepared by mixing an exfoliated phenylisocyanate-treated graphite oxide sheet with polystyrene, followed by chemical reduction with dimethylhydrazine. Glucose oxidase was immobilized on this composite via electrostatic interaction using a layer-by-layer adsorption technique, with poly(diallyldimethylammonium chloride) as the counter-ionic material. A quartz crystal microbalance was used to estimate the amount of the adsorbed layer material. An amperometric glucose biosensor, fabricated with the glucose oxidase-immobilized graphene-polystyrene composite as a working electrode, showed significantly improved efficacy for measuring glucose concentration.