To provide a coherent jet system producing the effective coherent gas jet without needing a lance expanding part defining a recirculation area to a gas jetted from a lance, or the other component.

The gas jet 5 is allowed to flow out from nozzles 2 accommodated in the lance 3 having a lance face 6, the fuel is allowed to flow out from a first ring 30 composed of a plurality of openings around the nozzles 2 of the lance face 6, an oxidant is allowed to flow out from a second ring 31 composed of a plurality of openings respectively aligned to each opening of the first ring 30 at an outer side of the first ring 30, and the fuel and oxidant are burnt to create the frame envelop 24 around the gas jet 5.