The invention relates to a device for separating liquid or solid particles from an aerosol stream, comprising an impactor with a perforated disc (20) through which air flows and an impact plate (22) arranged at a short distance therebehind. The side against which air flows comprises a separating layer (24) with open structure. For the separating device to have a constantly good separating effect during operation, the perforated disc (20) is provided with spacer elements (50) on the back side thereof that lie against the region of flow of the separating layer, wherein the height of the spacer elements, the support surfaces for the separating layer (24) formed by the spacer elements (50) and the number and arrangement of the spacer elements (50) are selected depending on the material of theseparating layer (24) in such a way that during operation the holes (20a) of the perforated disc (20) remain free of the material of the separating layer (24).