Bending operation knobs, a first switch button provided in a first surface, and a second switch button provided side by side with the first switch button in the first surface and positioned on the side distant from the bending operation knobs relative to the first switch button are included. The second switch button is formed so as to have an outer diameter smaller than that of the first switch button, an outer circumferential side of the second switch button is covered by a fitting portion, and a projection portion is formed at a site of the fitting portion, the site facing the first switch button, on an outer circumference of the second switch button, the projection portion projecting toward the side away from the first surface relative to another site of the fitting portion.
