A sealing device for a medical instrument includes a fastening area and a sealing area designed to either bear on the circumference of a medical instrument inserted into the sealing device or to close the sealing device when no medical instrument is inserted. The sealing device further includes a first elastic wall enclosing the sealing area in a ring shape, with an annular first edge, which is connected to the sealing area, and an annular second edge, and a second elastic wall which encloses the first wall in a ring shape and is spaced apart therefrom, with an annular first edge and an annular second edge, which is connected to the fastening area.
