Abstract: A method and an apparatus in a plant for fibrating molten mineral material which in the form of a stream of molten material (4) is discharged to the peripheral surface of a primary spinner wheel (1) and which is formed to mineral fibres by being thrown out from the spinner wheel or from several cooperating spinner wheels. The distribution of the stream of molten material (4) over the width or length of the primary spinner wheel is improved in that a force is applied to the incoming stream of molten material (4), especially from rear side thereof as seen in the rotation direction of the spinner wheel, which force is acting in a plane substantially perpendicular to a generatrix to the peripheral surface of the spinner wheel (1) and in a blunt angle to the stream of molten material (4).