The invention relates to a separating device (3) and to a separating method for separating weed seeds and lost crops from the wastage outflow (102) of a harvesting machine (1). The separating device (3) is arranged on the harvesting machine (1) to the outlet area for the wastage (2) of the harvesting machine (1) and has at least one rotating separating element (31), with which a material stream substantially consisting of weed seeds and lost crops is separated from the wastage outflow (102) of the harvesting machine (1). The remaining material stream (103) substantially consists of non-grain constituents and can be spread back directly onto the field, while the separated material stream substantially consisting of weed seeds and lost crops can first be collected and e.g. rendered unable to germinate.