A distal end bending piece subjected to processing for fastening a nail-plate portion so as to allow seesaw movements is assembled on a proximal end side of a distal end rigid portion, a sleeve is inserted from a rear side, and the sleeve is fitted and fixed to the distal end rigid portion in a state where a distal end bending piece is housed in the sleeve, thereby allowing a first nail-plate portion to elastically press an inner circumferential surface of the sleeve and allowing a second nail-plate portion to elastically press a bottom surface of a recessed portion of the distal end rigid portion at a predetermined contact pressure. Such a configuration enables a secure and stable electrical conduction between the distal end rigid portion and the distal end bending piece without interfering with a reduction in a diameter of the insertion portion.