The invention relates to a method for manufacturing a fin (4) of width l and comprising corrugations (20) for a heat exchanger comprising at least one step of splitting a metal sheet (2) into at least two strips (4) of width l and a step of folding the strips (4) of width l in order to obtain the corrugations (20). The steps of splitting and of folding the metal sheet (2) take place simultaneously. A further subject of the invention is a device for applying such a method and a fin and a heat exchanger obtained by such a method, particularly for use in the motor-vehicle field.