In a living body introduction apparatus, an inner rotating cylinder is covered with a stretchable cover having an inner circumferential length shorter than an outer circumferential length of the inner rotating cylinder. A portion of the cover pushed out in a protruding form by a roller disposed on an outer circumferential surface of the inner rotating cylinder enters a circular groove formed inside an outer rotating cylinder. Rotation of the inner rotating cylinder circularly moves the protruding portion on the outer circumferential surface. The protruding cover portion pushes the circular groove to rotate the outer rotating cylinder. 生体内導入装置は、内回転筒の外周長よりも短い内周長の伸縮性を有するカバーで内回転筒を被覆し、内回転筒の外周面に配置されたローラにより凸状に押し出されたカバー部分が外回転筒の内側に形成された円形溝に入り込む。内回転筒の回転により凸状のカバー部分が外周面上を周回し、凸状のカバー部分が円形溝を推し進めることで、外回転筒を回転させる。
