The passive bending portion 24 for the endoscope 10 is disposed between the active bending portion 23 of the insertion portion 20 and the flexible tube portion 25 of the insertion portion 20 and is passively bent by receiving an external force. In the passive bending portion 24, the curvature gradually increases from the distal end portion of the passive bending portion 24 toward the proximal end portion of the passive bending portion 24.内視鏡10のための受動湾曲部24は、挿入部20の能動湾曲部23と挿入部20の可撓管部25との間に配設され、外力を受けることによって受動的に曲がる。受動湾曲部24において、曲率が受動湾曲部24の先端部から受動湾曲部24の基端部に向けて徐々に大きくなっている。
