A first annular surface 62a formed at a predetermined position on the distal end side and a second annular surface 62b having a diameter different from that of the first annular surface formed adjacent to the proximal end side of the first annular surface 62a A first fixing portion 69a which is tightly fixed to the first annular surface 62a, a second fixing portion 69b which is tightly fixed to the second annular surface 62b, and a second fixing portion 69b which is closer to the second fixing portion 69b than the second fixing portion 69b And a cover portion (outer peripheral wall portion 66, valley portion 67, and inner peripheral wall portion 68) that extends toward the end side and surrounds the bending operation lever 47 in a watertight manner.先端側の所定の位置に形成された第1環状面62aと、第1環状面62aの基端側に隣接して形成された第1環状面とは異径の第2環状面62bと、を有する湾曲操作レバー47に対し、第1環状面62aに密着固定される第1固定部69aと、第2環状面62bに密着固定される第2固定部69bと、第2固定部69bよりも基端側に延設されて湾曲操作レバー47を囲繞するカバー部(外周壁部66、谷部67、及び、内周壁部68)と、と有する弾性カバー48を水密に連結する。
