To provide a jet nozzle for a water jet propulsion system in which the propulsion force by the negative pressure immediately behind the nozzle port of the jet nozzle is hardly dropped even when the water jet propulsion system is increased in size.

In the jet nozzle X for the water jet propulsion system used for a ship, the nozzle port 11 of the jet nozzle X are formed in the air in a vicinity of a water level. Two or more nozzle ports are formed on the fore end side with respect to one flow passage of water flow fed from a pump. The nozzle ports are separated by the predetermined distance, and an air flow passage is formed between the nozzle ports.