An injector includes a nozzle hole, a needle, an actuator, a piston that is displaced in an axial direction according to extension or contraction of the actuator, an outer sleeve holding the piston slidably on its outer circumferential side and defining a pressure chamber expanded or shrunk according to displacement of the piston. When fuel pressure in the pressure chamber is increased upon extension of the actuator, the needle opens the nozzle hole. The injector further includes an inner sleeve slidably fitted around the needle and received in the pressure chamber, an urging device for urging the inner sleeve in the axial direction and for increasing or decreasing its urging force according to displacement of the piston, an engagement surface, and a fuel chamber. A gap between the fuel chamber and the pressure chamber is closed or opened when the inner sleeve annularly engages or disengages from the surface, respectively.