A rocuronium bromide injection solution-prefilled syringe (1) of the present invention includes a syringe (2) comprising an outer cylinder (21) made of synthetic resin, a gasket (22) which is accommodated inside the outer cylinder (21) and liquid-tightly slidable inside the outer cylinder, and a seal member (23) for sealing a distal end opening of the outer cylinder (21)； and a rocuronium bromide injection solution (3) filled inside the syringe (2). The gasket (22) 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.
