Provided is an endoscope which is capable of letting a liquid drain off to a satisfactory level at the time of cleaning, while securing the degree of freedom of a layout. An observation window is placed on an observation window base part which is formed on a distal end surface of a distal end part so as to protrude from the surrounding area. An outer peripheral shape of the observation window base part is formed into a streamline shape with respect to a flow of a cleaning fluid jetted from a nozzle. With this feature, it is possible to block a liquid flow having a low flow rate from flowing on the observation window, and to allow the liquid flow which has been used for cleaning to promptly move to the outside of the observation window.