An attachment for an endoscope attachable to and detachable from an endoscope head body which is provided on a distal side of an insertion portion of an endoscope, the attachment for the endoscope comprising: a flat protrusion; an Albarran lever pivotally supported by the flat protrusion; and a housing sheath part, the housing sheath part comprising a sheath which is detachably attached to the endoscope head body, wherein the housing sheath part has, on an inner circumferential side, a housing sheath flattening which is adapted to a flattening of the endoscope head body which is a plane surface such that when the housing sheath part is placed on the endoscope head body, the housing sheath flattening abuts against the flattening, wherein the flat protrusion is formed on the housing sheath flattening, wherein the flat protrusion extends radially inwards in the sheath perpendicularly to the housing sheath flattening and projects into an Albarran lever chamber of the endoscope when the housing sheath part is arranged on the endoscope head body, wherein the sheath is provided with a tool opening, through which tool opening a tool can project laterally from the endoscope head body when the housing sheath part is placed on the endoscope head body, wherein the Albarran lever is disposed to face the tool opening, wherein the housing sheath flattening is adjacent to the tool opening and wherein the sheath is a hollow cylinder that is open at an attachment opening provided along a longitudinal direction of the hollow cylinder through which an outer circumferential portion of the endoscope head body can be placed for attachment thereto, wherein the tool opening is cut out in a U-shape, and wherein the tool opening is disposed at a location facing the attachment opening. a flat protrusion; an Albarran lever pivotally supported by the flat protrusion; and a housing sheath part, the housing sheath part comprising a sheath which is detachably attached to the endoscope head body, wherein the housing sheath part has, on an inner circumferential side, a housing sheath flattening which is adapted to a flattening of the endoscope head body which is a plane surface such that when the housing sheath part is placed on the endoscope head body, the housing sheath flattening abuts against the flattening, wherein the flat protrusion is formed on the housing sheath flattening, wherein the flat protrusion extends radially inwards in the sheath perpendicularly to the housing sheath flattening and projects into an Albarran lever chamber of the endoscope when the housing sheath part is arranged on the endoscope head body, wherein the sheath is provided with a tool opening, through which tool opening a tool can project laterally from the endoscope head body when the housing sheath part is placed on the endoscope head body, wherein the Albarran lever is disposed to face the tool opening, wherein the housing sheath flattening is adjacent to the tool opening and wherein the sheath is a hollow cylinder that is open at an attachment opening provided along a longitudinal direction of the hollow cylinder through which an outer circumferential portion of the endoscope head body can be placed for attachment thereto, wherein the tool opening is cut out in a U-shape, and wherein the tool opening is disposed at a location facing the attachment opening.