A rocuronium bromide injection solution-prefilled syringe of the present invention includes a syringe comprising an outer cylinder made of synthetic resin, a gasket which is accommodated inside the outer cylinder and liquid-tightly slidable inside the outer cylinder, and a seal member for sealing a distal end opening of the outer cylinder； and a rocuronium bromide injection solution filled inside the syringe. The gasket is formed by vulcanized chlorinated butyl rubber added calcined clay, and said calcined clay is only added as an inorganic filler classified as an inorganic reinforcing agent and an inorganic filling agent.
