FUEL INJECTION VALVE

An object of the present invention is to improve the exhaust emission for a fuel injection valve having a stepped injection hole constructed so that a small diameter portion and a large diameter portion are communicated with each other with a stepped portion intervening therebetween. The present invention resides in a fuel injection valve comprising a cylindrical nozzle body which has a tip portion formed to have a conical shape, an injection hole which penetrates from an inner circumferential surface to an outer circumferential surface of the nozzle body, the injection hole being constructed so that a small diameter portion, which is positioned on a side of the inner circumferential surface of the nozzle body, is communicated with a large diameter portion which is positioned on a side of the outer circumferential surface of the nozzle body, with a stepped portion intervening therebetween, and a valve plug which is accommodated slidably in the nozzle body and which opens/closes the injection hole, wherein a ratio of the hole diameter of the large diameter portion with respect to the hole diameter of the small diameter portion is not less than 3.1 and not more than 4.0, a ratio of a length of the large diameter portion with respect to a length of the small diameter portion is not less than 0.25 and not more than 0.55, and a ratio of the length of the large diameter portion with respect to the hole diameter of the large diameter portion is not less than 0.4 and not more than 1.6.