An endoscope apparatus provided with an insertion aid (50) through whose base end of an insert part (12) of the endoscope (10) is inserted and whose tip (58) is fitted with a balloon (30), the balloon (30) being closely adhered to a body cavity by being inflated, wherein the outer circumferential face of the insertion aid (50) is coated with a lubricating coat material, and the friction coefficient of the outer circumferential face of the insertion aid (50) is set to 5 to 30% of the friction coefficient of the balloon (30).
