Bending operation mechanism of endoscope

A bending operation mechanism of an endoscope includes a bending operation lever, a seal unit having a tubular member and an elastic member. The elastic member has a fixed part attached to an outer circumference of the tubular member in a circumferential manner along a longitudinal axis direction N of the tubular member. An extending part that extends from an outer circumference of the fixed part to the outside of the fixed part in a radial direction K into a shape of a circle substantially concentric with the fixed part. A region extends from the outer circumference of the fixed part would extend with a predetermined angle.