To provide a reverser device which can exhibit high performance at the time of going astern in a water jet propulsion ship.

In a water jet propulsion ship, the jetting cylinder of a reversing jet from a reverser 9 formed at the jetting opening 8 of a water jet is formed into a fork shape, and the jetting opening 10 of the jetting cylinder is opened in such a direction as deviated to the side for a jet generator. It is thus possible to activate the reversed water jet efficiently without hitting the casing of the jet generator.