Abstract: A prefilled syringe is capable of separate storage of different substances before use. It includes a tubular body having an injection needle at one end and a plunger at the other end, and a partition axially slidable in the tubular body. The partition includes a front part and a rear part independent of each other, and as a whole divides the interior space of the tubular body into a front compartment and a rear compartment in a sealing manner for storing mutually different substances. A bypass is disposed generally between the front and rear compartments to introduce the substance in the rear compartment into the front compartment when the partition is slid under pressure provided by the plunger to be adjacent to the bypass to thereby mix the substances immediately prior to injection.