An endoscope includes a flexible portion extended to a part on a proximal direction side of an insertion main body along a longitudinal axis, and a passive bending portion provided to a distal direction side of the flexible portion in the insertion main body, being more flexible than the flexible portion, and configured to passively bend when external force acts thereon. The endoscope includes an attachment unit which includes a fin portion spirally extended along the longitudinal axis, and through which the insertion section is inserted, and a holding portion provided to the insertion main body, and configured to hold the attachment unit in a state that the attachment unit covers the passive bending portion and that the attachment unit is rotatable about the longitudinal axis with respect to the insertion main body.