A cleaning device for a laboratory fermenter for growing microorganisms is provided. The laboratory fermenter to be cleaned has a gas supply connection connected to a line reaching into the fermenter's nutrient solution, an exhaust connection to the gas space over the nutrient solution, and a withdrawal connection leading to the fermenter's deepest point. The cleaning device includes three cleaning connections, an immersion pipe connection and two gas connections. Flow in each gas connection is controlled via intermediate switch valves having a cleaning start position and a cleaning end position. The cleaning connections are connected via hose lines to hose pinch control valves, a hose pinch pump, at least one filter. A cleaning control manages the cleaning process by controlling flow from and/or to an air connection, a water connection and a waste water connection. The cleaning controller may also control introduction of acids and/or bases.