One of a first endoscopic treatment instrument setting state and a second endoscopic treatment instrument setting state is selectable. In the former state, when a first diathermic snare is removably inserted in a flexible tube, a loop portion is circumferentially broadened and disposed along a first projection portion. In the latter state, when a second diathermic snare is removably inserted in the flexible tube, a loop portion is circumferentially broadened and disposed along a second projection portion.
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