The invention refers to a housing sheath attachable to and detachable from an endoscope head body, which is provided on a distal side of an insertion portion of an endoscope. The housing sheath comprises: a sheath that is a hollow cylinder open at an attachment opening provided along a longitudinal direction of the hollow cylinder, and is provided with a tool opening cut out in a U-shape at a location facing the attachment opening; and an Albarran lever that is rotatably supported inside the sheath.