Pressurized fuel of a common rail is introduced into a control chamber of a fuel injector. An electromagnetic valve opens or closes a fuel discharge passage of the control chamber to adjust a hydraulic pressure of the control chamber. Through a switching leak passage, bubble-containing fuel directly returns from a valve opening of the electromagnetic valve to a low-pressure return passage without passing through an armature chamber. Through a stationary leak passage, the fuel leaking from every slide portion returns to the return passage via the armature chamber. A downstream portion of the stationary leak passage opens to the upper portion of the armature chamber. A damper element is provided downstream of the electromagnetic valve in the return passage for canceling an increased fuel pressure.