To provide a high frequency treatment instrument for an endoscope, wherein a curved part formed at the distal end of a flexible sheath tube can be safely bent by remote control without generating problems on electric insulation from a conductive operation wire and strength or the like.

The curved part 2 freely bendable by external force is formed at a part near the distal end of the flexible sheath tube 1, the distal end of an electrically insulating flexible tube 8 for operations inserted and disposed inside the flexible sheath tube 1 in the state of surrounding the conductive operation wire 7 is connected to the vicinity of the distal end of the curved part 2, and by operating the flexible tube 8 for operations from the proximal end side, the curved part 2 is bent.