Regarding a blade inspection system, each of endo scope guide devices for a borescope has an insertion portion guide tube for guiding an insertion portion and a first fixing portion which is provided on the insertion portion guide tube and fixes the insertion portion guide tube in a corresponding external access port. When the insertion portion is attached into the insertion portion guide tube, lengths of extending portions of the endoscope guide devices are different between the plurality of endoscope guide devices extending from the corresponding external access port so that a position for observing a predetermined portion of a blade by an observation optical system of the insertion portion comes to a position determined in advance for each of the corresponding external access ports.