PURPOSE: To enlarge the range of controllable fuel injection quantity by providing, on the tip of a body, a measuring member provided with plural holes bored therein for injecting fuel therethrough and an opening/closing member for opening/closing the holes in such a way as to be capable of relatively displacing, and attaching a drive means for relatively displacing both members.

CONSTITUTION: In a fuel injector 10, the injection quantity thereof varies dependent upon variation in the number of a hole (injection port) 14a of a perforated plate 14, so the number of openings in the hole 14a disposed on the perforated plate 14 is varied in accordance with a relative change between the perforated plate 14 serving as a measuring member and a cap 13 serving as an opening/ closing member on the tip portion of a body 1, thereby varying injection quantity performance. That is, the number of the opening holes on the perforated plate 14 is varied so that the injection quantity performance is selected, thereby achieving the injection quantity over a wide range as a whole so as to enlarge the range of fuel injection quantity where the fuel injector 10 can be controlled.