A first bendable section (41) which can be bent in an arbitrary direction and a second bendable section (42) which can be bent in the bending direction of this first bendable section (41) are provided at the tip end side of an insertion portion (7). A balloon (38) which is inflated/contracted by feed/discharge of a fluid is provided in this second bendable section (42) so that hardness of this second bendable section (42) can be varied and insertion work into a curved portion is facilitated.
