Jet mill

The invention discloses a jet mill which comprises a flow conduit for communicating a cyclone separator with a filter, wherein the flow conduit comprises a plurality of pipe sections; every two adjacent pipe sections are communicated by a reducing pipe; one end of each reducing pipe, which is provided with a small opening, is close to the filter. According to the jet mill provided by the invention, by dividing the flow conduit into a plurality of sections and additionally arranging the reducing pipes to replace an original flow conduit which is of an integrated structure and has a uniform diameter, the flow conduit has an intercepting effect on superfine powder, so that the output of the superfine powder entering the filter to be separated is reduced, the output ratio of the superfine powder is kept in the range of 0.5 weight percent, the output of the superfine powder is obviously reduced and the superfine powder with low output does not need to be processed again, and thus, a production process of sintering neodymium iron boron is simplified, a safety accident is avoided and meanwhile, production cost is also reduced.