NOVELTY - The device comprises: a treatment chamber (20), in which a treatment liquid is stored up to a bath level (M); a supplying unit (7) for supplying treatment liquid in the treatment chamber; a transport device, through which a flat material to be treated in a horizontal position in a transport plane below the bath level is transported to the treatment chamber; a portion for collecting the treatment liquid; and a discharge device (40) provided with a discharge opening (41) to convey the treatment liquid from the treatment chamber at a removal rate to the collecting portion.    USE - The device is useful for chemically or electrolytically treating a flat material to be treated with a treatment liquid (claimed), where the flat material comprises a printed circuit board, a semiconductor wafer, a glass plate, a photoelectric cell such as a photoelectric solar cell, and a screen plate.    ADVANTAGE - The cost-effective device is capable of chemically or electrolytically treating the flat material without any deformation and damage, ensures uniform action of the treatment liquid on an entire surface of the material, and has easy maintenance and simple construction.    DETAILED DESCRIPTION - The device comprises: a treatment chamber (20), in which a treatment liquid is stored up to a bath level (M); a supplying unit (7) for supplying treatment liquid in the treatment chamber; a transport device, through which a flat material to be treated in a horizontal position in a transport plane below the bath level is transported to the treatment chamber; a portion for collecting the treatment liquid; and a discharge device (40) provided with a discharge opening (41) to convey the treatment liquid from the treatment chamber at a removal rate to the collecting portion. The discharge device comprises a control device through which a discharge rate of the treatment liquid through the discharge opening is adjustable. The bath level is adjustable by the control device. The discharge device further comprises a discharge channel. The control device further comprises a control element consisting of a pump, and a drive, which is arranged in the control element. A cross-section of the discharge channel comprises a changing element. The changing element comprises a valve, a flap and a slider. The removal rate is more adjustable by the drainage channel. The discharge channel is below a liquid level in collection area ends. The discharge device comprises a discharge line, which defines an outflow channel. An aperture is formed between the treatment chamber and the discharge device. A discharge space is formed between the aperture and the discharge opening. The aperture comprises an opening for the passage of the treatment liquid into the discharge space. The aperture partly forms a bottom of the treatment space and extends parallel to a bottom wall of the discharge space, so that a passage gap is formed between the bottom wall of the discharge space and the aperture. The aperture is formed by end plates arranged in the bottom wall of the discharge space facing a guide element, so that a through-gap is formed between the lower wall of the discharge space and the guide element. Passage spacings at locations of the guide element adjacent to the discharge opening are smaller than at other points of the guide element and away from to the discharge opening. An INDEPENDENT CLAIM is included for a method for chemically or electrolytically treating a flat material to be treated with a treatment liquid.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a device for chemically or electrolytically treating a flat material to be treated with a treatment liquid.    Supplying unit (7)    Treatment chamber (20)    Discharge device (40)    Discharge opening (41)    Bath level. (M)