A medical instrument holding apparatus includes an attachment device attached to a longitudinal shaft and having a casing, a coupling device attached to the casing of the attachment device, and a carrying device attached to the coupling device, and the carrying device includes an orifice and an aperture, and the aperture of the carrying device is tilted and inclined relative to the orifice of the carrying device, a medical instrument includes an insertion tube engaged into the orifice of the carrying device, and a projecting device is engaged in the aperture of the carrying device for projecting a light onto the insertion tube of the medical instrument at an index mark.