A disposable syringe includes a barrel with a bushing unit disposed on an inner surrounding surface thereof, a tubular grip unit in fluid-tight engagement with the bushing unit for holding a needle seat, a tubular plunger having a seal ring that is slidable on and in fluid-tight frictional engagement with the bushing unit so as to cooperate with the grip unit to define a medicament chamber, and a shield plug member in fluid-tight engagement with the grip unit and having a duct that communicates a needle cannula with the medicament chamber, thereby ensuring fluid-tightness of the medicament chamber.
