NOVELTY - An adhesive agent includes a main component, a crosslinking agent, an adhesiveness-improvement agent, and a reaction catalyst. The adhesive agent has a torque-time ratio of 30-80 seconds as measured by vibration curing test of JIS K 6300-2 at a curing temperature of 160 degrees C.    USE - Adhesive agent is used for joining solid polymer electrolyte membrane and gas-diffusion layer in membrane-electrode structures (claimed) used in polymer electrolyte fuel cells of two-wheeled/four-wheeled motor vehicles and portable power supplies.    ADVANTAGE - The adhesive agent forms adhesive layers which can be re-stuck even when the components deviate during manufacture of membrane-electrode structure. The adhesive agent enables manufacture of membrane-electrode structures with high yield and quality.    DETAILED DESCRIPTION - An adhesive agent includes a main component, a crosslinking agent, an adhesiveness-improvement agent, and a reaction catalyst. The adhesive agent has a torque-time ratio of 30-80 seconds as measured by vibration curing test of JIS K 6300-2 at a curing temperature of 160 degrees C. The ratio is defined as the ratio of time until torque reaches Ml+0.1x (Mh-Ml) and time until torque reaches Ml+0.9x (Mh-Ml), where Mh is maximum value of torque and Ml is minimum value of torque. An INDEPENDENT CLAIM is included for membrane-electrode structure (10) consisting of a solid polymer electrolyte membrane (11), catalyst layers (12,13) laminated on the surface(s) of the electrolyte membrane, a gas-diffusion layer (15) laminated on the catalyst layer, and an adhesive layer (14) provided in the outer periphery of the catalyst layer for joining the electrolyte membrane and gas-diffusion layer. The adhesive layer contains the adhesive agent.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the membrane-electrode structure.    Membrane-electrode structure (10)    Solid polymer electrolyte membrane (11)    Catalyst layers (12,13)    Adhesive layer (14)    Gas-diffusion layer (15)