To provide a jet fan device capable of being made small in size, and of obtaining powerful thrust by combining a plurality of small jet fans with one another in a fan jet propelled boat.

In a fan jet propelled boat, a plurality of small jet fans are provided for a supporting frame capable of supporting a large sized jet fan in such a way that those small jet fans are positioned within the diameter of the large sized jet fan capable of being housed therein, and those small jet fans are connected with a driving unit mounted to a hull 1 so as to be interlocked therewith. As compared with the installation of a single large sized jet fan, the small jet fans high in revolution can easily be provided so as to permit the boat to sail at the high speed.