Abstract: A method for adjusting the fuel injection quantity of an electromagnetic fuel injector having a needle valve, an electromagnetic actuator composed of a movable core which moves with the needle valve and a fixed iron core for attracting the movable core to move the needle valve to its open position, an adjust pipe inserted within a through hole of the fixed iron core, and a spring interposed between the adjust pipe and the movable core for continuously biasing the needle valve to its closed position, has the steps of inserting the adjust pipe into the through hole of the fixed iron core by a predetermined length and temporarily fixing the adjust pipe to the fixed iron core so as not to be moved by a force received from the spring when the needle valve is operated and so as to start moving when a force larger than the above described force of the spring is applied, running in the injector for a predetermined period of time, finely adjusting the position of the adjust pipe while checking the actual fuel injectio