Bending operation knobs 11 and 12, a first switch button 21 provided in a first surface 4f, and a second switch button 22 provided side by side with the first switch button 21 in the first surface 4f and positioned on the side distant from the bending operation knobs 11 and 12 relative to the first switch button 21 are included. An outer circumferential side of the second switch button 22 is covered by a fitting portion 7, and a projection portion 7t is formed at a site of the fitting portion 7, the site facing the first switch button 21, on an outer circumference of the second switch button 22, the projection portion 7t projecting toward the side away from the first surface 4f relative to another site 7a of the fitting portion 7.
