The rear end side of treatment equipment-side duct which enables treatment equipment provided within an insertion unit to be inserted, and which also serves as a suction duct, is disposed generally in parallel with the tip side of a suction-side duct extending forward from a universal cable side so as to be an opening end, and both opening ends are detachably attached with a filter unit in which a forceps plug portion serving as a suction duct opening, and a filter portion for retrieving (storing) tissue by suction are provided, and a suction switchover valve for performing a suction switchover operation is provided at the backward side thereof, thereby enabling retrieval of tissue without influence of the periphery of the suction switchover valve. Thus, defects due to a long duct can be eliminated, and tissue can be retrieved without influence of the periphery of the suction switchover valve.
