Prestroke Adjustment Method for Fuel Injection Valve

Provided is a prestroke adjustment method for a fuel injection valve capable of reducing variations in a prestroke amount regardless of the level of machining accuracy of a component. The prestroke adjustment method adjusts a prestroke amount D2 of a fuel injection valve including a gap forming member that forms a gap G2 defining a prestroke between a valve member and engagement portions and of a movable core by a second portion abutting on the movable core in a state where a first portion is positioned at a reference position of the valve member In the prestroke adjustment method, a load L in the direction from the first portion toward the reference position of the valve member is applied to the gap forming member assembled to the valve member to plastically deform the gap forming member thereby shortening the relative length between the first portion and the second portion and setting the prestroke amount D2 to the target value T2.