PROBLEM TO BE SOLVED: To provide a prefilled syringe capable of surely preventing liquid leakage during the work of mounting a plunger on a gasket.SOLUTION: The prefilled syringe 1 includes a prefilled syringe body 10 having a gasket 3 in the inside, and a plunger 4. The plunger 4 includes a distal end part 41, a plunger side screw part 42 provided on the outer surface, and a pressurizing projection part 43. The gasket 3 includes a spiral screw part 66 to be screwed with the plunger side screw part, an annular recessed part 64 for housing the pressurizing projection part 43, and a pressurized projection part 65 to be pressurized by the pressurizing projection part 43. When screwing of the gasket 3 and the plunger 4 advances, the pressurizing projection part 43 pressurizes the pressurized projection part 65 in a distal end direction, the plunger side screw part 42 is brought into press contact with the spiral screw part 66 and pressurizes it in a rear end direction, and the movement of the gasket is prevented.
