A concentrate burner for feeding a pulverous concentrate mixture and reaction gas into a reaction shaft of a flash smelting furnace. The concentrate burner includes a feeder pipe for feeding a concentrate mixture into the reaction shaft and a dispersing device for directing dispersing gas to the concentrate mixture flowing around the dispersing device. For feeding the reaction gas into the reaction shaft, a gas supply device is provided which includes a reaction gas chamber for mixing the reaction gas with the concentrate mixture, and for directing the concentrate mixture to the side by the dispersing gas. The reaction gas chamber includes a turbulent flow chamber, to which an inlet channel opens tangentially for directing the reaction gas to the reaction gas chamber in a tangential direction. In the inlet channel, an adjusting member is arranged for adjusting the cross-sectional area of the reaction gas flow.