The endoscope 2 includes a flexible tube portion 4 having flexible tubes 4 a, 4 b, and 4 c, a motor 72 disposed on the proximal end side of the flexible tube portion 4, and a flexible tube portion 4 disposed on the distal end side of the flexible tube portion 4 A drive force transmission unit 53, a drive shaft (not shown) disposed along the longitudinal axis in the flexible tube portion 4 and rotated about the longitudinal axis by the driving force of the motor 72, and transmitting the rotation of the motor 72 to the drive force transmission unit 53 79. The twisting resistance around the longitudinal axis of the flexible tube portion 4 is more than the twisting resistance from the relay gear 75 of the motor 72 through the drive shaft 79 to the drive gear 55 of the driving force transmission unit 53 high.内視鏡2は、蛇管4a,4b,4cを有する可撓管部4と、可撓管部4の基端側に配置されるモーター72と、可撓管部4の先端側に配置される駆動力伝達ユニット53と、可撓管部4内に長軸に沿って設けられ、モーター72の駆動力によって長軸周りに回転されてモーター72の回転を駆動力伝達ユニット53に伝達する駆動シャフト79と、を具備し、前記可撓管部4の長軸周りの捻り耐性を、モーター72の中継歯車75から駆動シャフト79を介して駆動力伝達ユニット53の駆動歯車55までに至る捻り耐性より高い。
