PROBLEM TO BE SOLVED: To provide an endoscope for preventing a droplet from remaining in an illumination window.SOLUTION: A air/water sending nozzle 33, a treatment tool outlet 38, an observation window 45, a pair of illumination windows 46, 47, and an expansion opening 55 are arranged on the flat surface 50 of an insertion part of an endoscope. The treatment tool outlet 38 has a first circular contour part 60. The expansion opening 55 has a second contour part 61, both sides of which are connected to the first contour part 60 and the center of which is expanded toward the observation window 45. The second contour part 61 is in crescent shape so as to reduce the area of the flat surface 50 existing in a region 59 surrounded by the air/water sending nozzle 33, the treatment tool outlet 38, and the observation window 45. Water droplets remaining on the flat surface 50 of the region 59 are captured by the expansion opening 55. Air injection from the air/water sending nozzle 33 prevents water droplets from being sent to the illumination window 46 located separately from the air/water sending nozzle 33.
