A fluidised bed opposed jet mill to produce ultrafine particles from a feed material of low bulk density with a housing in vertical design, with a product feed point and a product discharge, with a grinding zone located in the lower area of the housing which has grinding nozzles spaced evenly around the circumference whose jets intersect at one central point and with a classifying device installed in the upper area of the housing wherein the feed material is dosed as a gas-particle mixture from below into a sump of the fluidised bed opposed jet mill whereby a deflector hood is fitted above the feed point and below the grinding nozzle level, and the grinding nozzles are designed to be flush with the wall.