An injector comprises an injection nozzle 1 having a nozzle hole 3, a valve body 2 for controlling a fuel flow through the nozzle hole 3, and changing means 6, 7, 10, 11, 12, 13, 20 for changing a shape of fuel spray, the fuel spray being formed by the fuel which flows through the nozzle hole. The injector includes rotation preventing means for preventing the valve body 2 from rotating with respect to the injection nozzle 1 around a center axis of the valve body 2. The injector includes angular displacement controlling means for controlling an angular displacement of the valve body 2 with respect to the injection nozzle 1. A shape of a tip of the valve body 2 is circumferencially non-uniform.