A device is used for cleaning a flexible hollow shaft of a medical instrument, the wall of said flexible hollow shaft is provided with openings. The device comprises a hollow space in which at least one portion of said hollow shaft can be received. A cleaning liquid can be delivered into said hollow space via an attachment piece. An inside wall of said hollow space is at a radial distance from the outer face of said hollow shaft. Flow resistance means, spaced axially apart from one another, are provided, either in the form of sealing means or in the form of narrow annular gaps which respectively seal off or delimit, in the axial direction, a space between said outer face of said hollow shaft and said inside wall of said hollow space.