The endoscope apparatus is provided with a function part which is provided in the endoscope and has a first function and a second function which exerts a greater amount of force than the first function, a rotational driving force for operating the functional part A drive unit provided in the endoscope and driven in accordance with the rotational driving force to operate the functional unit, and a drive shaft having a drive shaft and rotatable around the drive shaft , The torsional rigidity in the first rotational direction corresponding to the first function is higher than the torsional rigidity in the second rotational direction corresponding to the second function than the torsional rigidity in the first rotational direction corresponding to the first function And a drive shaft for transmitting a rotational driving force from the driving unit to the driving mechanism unit.内視鏡装置は、内視鏡に設けられ、第1の機能及び該第1の機能よりも多くの力量がかかる第2の機能を有する機能部と、機能部を作動させるための回転駆動力を発生させる駆動部と、内視鏡に設けられ、回転駆動力に応じて駆動し、機能部を作動させるための駆動機構部と、駆動軸を有し、該駆動軸回りに回転可能であり、第1の機能に対応する第1の回転方向に対する捻れ剛性よりも、該第1の回転方向とは逆方向であって第2の機能に対応する第2の回転方向の捻れ剛性が高く設定され、駆動部から駆動機構部へ回転駆動力を伝達させる駆動シャフトと、を具備する。
