An endoscope includes an insertion portion, a distal end rigid member, and a channel tube. The distal end rigid member is provided on a distal end side with respect to the bending portion of the insertion portion, and includes an illumination window, an observation window, and a treatment instrument opening. As the distal end rigid member moves relative to the bending portion in a distal end direction of a longitudinal axial direction, the distal end rigid member can change from a first state in which a distance between a proximal end surface of the distal end rigid member and a distal end surface of the bending portion is fixed to a first distance to a second state in which the distance is equal to a second distance longer than the first distance.