In an endoscope system including an endoscope having an insertion section to be inserted into a cavity under inspection, a bending portion which is provided in said insertion section near a distal end thereof and is bendable in at least two different directions and an operation section to which a proximal end of the insertion section is connected and a disposable protection cover having an insertion section cover for covering said insertion section of the endoscope and having formed therein an insertion section inserting channel into which said insertion section of the endoscope is insertable and at least one conduit channel, said insertion section and bending portion of the endoscope are formed to have a non-circular lateral cross section, a direction in which said non-circular cross section has a larger size is aligned with a direction in which said bending portion is bent by a maximum bending angle or a direction in which said non-circular cross section has a smaller size is aligned with a direction in which said bending portion is bent by a minimum bending angle.