PURPOSE: To provide a multistage injection type fuel injection nozzle which is constituted to reduce the number of parts and facilitate assembly.

CONSTITUTION: A fuel reservoir part 4, an injection nozzle 5, and a spring chamber 2 are formed in a nozzle body 1, and when a needle valve 7 lifted when a fuel pressure is increased to a value higher than a given value is arranged on the fuel reservoir part 4. A coil spring 15 is contained in the spring chamber and a pressure introduction chamber 10 to introduce fuel in the fuel reservoir part 4 to the needle valve 7 is provided. This constitution slidably contains a free piston 12 in the pressure introduction chamber 10, arranges a closing member 16 in the spring chamber 2, and provides a regulating part 20 which is brought into contact with the closing member 16 when the free piston 12 is lifted by a given amount and caused to regulate prelift.