Bonding jig

A bonding jig used for bonding a gas diffusion layer or a fuel cell constituent member including the gas diffusion layer to be sandwiched between separators and an adhesive sheet for joining the separators to the gas diffusion layer or fuel cell constituent member, the bonding jig being capable of simultaneously performing bonding and eliminating fluffy fibers on the gas diffusion layer. The bonding jig includes a loading area (recess) where the gas diffusion layer is loaded when the bonding is performed, and the recess has a plurality of communication holes that communicate with the outside and that are coupled to a suction pump. While the adhesive sheet is placed on the side of the upper face of the bonding jig so as to be integrated with the gas diffusion layer, the suction pump is actuated to eliminate fluffy fibers on the gas diffusion layer.