An endoscope includes: an elongated insertion section； a side observation window that includes a tapered part on a side circumference intersecting in a longitudinal axis direction of the insertion section, and includes a circumferential side surface formed in a cone shape； and a cleaning nozzle that includes an opening part through which liquid cleaning the circumferential side surface of the side observation window is ejected. The opening part is inclined to direct an ejection direction of the liquid toward a distal end of the tapered part. A center position of the opening part of the cleaning nozzle is provided on proximal end side with respect to a center position of the side observation window in the longitudinal axis direction.
