PROBLEM TO BE SOLVED: To provide an endoscope where draining property is improved by reliably prevent water flow from a water supply conduit to an air/water supply pipeline in switch into air supply operation following water supply operation, and where an insertion part of a thick diameter is prevented and can be thinned.SOLUTION: An endoscope 1 includes: a nozzle 11 that supplies air and water to a surface of an observation window 9 an air supply pipeline 13 connected to an air supply source 17 a water supply conduit 14 connected to a water supply source 18 an air/water supply pipeline 12 communicated with the nozzle 11 a merging section that extends so that the air/water supply pipeline 12 is communicated therewith at its leading end, and that is fitted so that the water supply conduit 14 is communicated and merging with from the side of the air supply conduit 13 at its proximal end. In the merging section, an open surface of the water supply pipeline 14 has an inner surface of the air supply pipeline 13 and a step of a specific length.
