The endoscope 1 includes an elongated insertion portion 4, a lateral observation window 26 having a peripheral side surface formed in a conical shape with a taper provided on the side periphery crossing the longitudinal axis direction of the insertion portion 4, a side And washing nozzles 28a and 28b which are provided inclining the jetting direction of the liquid for cleaning the peripheral side surface of the side observing window 26 toward the tapered tip end side.内視鏡1は、細長の挿入部4と、挿入部4の長手軸方向に交わる側方周囲に、テーパが設けられた錐形状に形成された周側面を有する側方観察窓26と、側方観察窓26の周側面を洗浄するための液体の噴出方向をテーパの先細りした先端側に向けて傾けて設けられた洗浄ノズル28a、28bと、を備える。
