A filter device for filtering oil leakage amounts from hydraulic systems, wherein hydraulic oil can be sucked from a tank (4) via a suction line (10) and leakage oil can be fed via a leakage oil line (12) to the non-filtered side of a leakage oil filter (16). Filtered leakage oil can be fed back from the filtered side (20) of the filter to the tank (4). The invention is characterized in that a valve assembly (26) is provided, by way of which a fluid connection (22, 30) can be released between the filtered side (20) of the leakage oil filter (16) and the suction line (10) in order to reduce the leakage oil pressure in the leakage oil line (12).