The visual field of an observation window is prevented from being interrupted by bubbles generated near a gas spray port when a constant-pressure gas supply is provided through an opening formed on the distal end surface of a flexible endoscope, thereby securing the field of vision. Accordingly, there is provided an endoscope gas feed system (2) comprising: a fluid curtain nozzle (54) for blowing a fluid curtain-forming gas toward an observation window provided on a distal end surface (44) of the insertion part (42) of an endoscope including at least the observation window (46) and an opening (50), (58) for spraying a constant-pressure feed gas and on an opposite side of the opening with respect to the observation window； a constant-pressure gas feed unit for supplying the constant-pressure feed gas, so as to spray the constant-pressure feed gas from the opening； and a fluid curtain-forming gas feed unit for supplying a gas, so as to blow the fluid curtain-forming gas from the fluid curtain nozzle.
