The invention relates to a method of feeding a fuel gas into the reaction shaft of a suspension smelting furnace and to a concentrate burner for feeding a reaction gas and fine solid matter into the reaction shaft of the suspension smelting furnace. In the method, fuel gas (16) is fed by the concentrate burner (4) to constitute part of the mixture formed by the pulverous solid matter (6) and the reaction gas (5), so that a mixture containing the pulverous solid matter (6), reaction gas (5) and fuel gas (6) is formed in the reaction shaft (2). The concentrate burner (4) comprises fuel gas feeding equipment (15) for adding the fuel gas (16) to constitute part of the mixture that is formed by fine solid matter (6) and reaction gas (5).