The present invention relates to a method for producing highly pure, granular silicon with a narrow particle-size distribution by decomposing silanes or halosilanes in a fluidised bed and epitaxially growing silicon on silicon seed particles, which method is characterised in that the gas containing silicon is supplied to the reaction chamber in an upward flow and the contents of the fluidised bed are separated in a continuous or discontinuous manner, whereby a particle stream from the fluidised bed is supplied to a separator mounted outside the fluidised bed, particles of the desired size are separated and undersized particles are returned to the fluidised bed. The invention also relates to a device and the use thereof for carrying out said method.