A blade inspection system configured to inspect a plurality of blades periodically disposed on a periphery of a rotating shaft of a rotor of an engine and rotated on the rotating shaft, comprising: an endoscope having an insertion portion in which an observation optical system (31, 32, 33, 35) is provided; and a plurality of guide devices (3, 4) configured to be attached to external access ports different from each other of the engine and configured to guide the insertion portion of the endoscope into the engine, wherein each of the guide devices (3, 4) has: a guide tube configured to guide the insertion portion; a first fixing portion which is provided on the guide tube and is configured to fix the guide tube in the corresponding external access port; and a second fixing portion configured to fix the insertion portion in an axial direction of the guide tube; and a rotational movement amount restricting mechanism portion (21a,21b,25A,81a,81b) which is provided in the guide tube and is configured to restrict a rotational movement amount of the insertion portion around the axial direction of the guide tube, wherein a length (L1,L2) of an extending portion of the guide device (3, 4), which is configured to extend from the corresponding external access port, is different among the plurality of guide devices (3, 4) so that, when the insertion portion is attached to the second fixing portion, a position for observing a predetermined portion of the blade by the observation optical system (31, 32, 33, 35) of the insertion portion comes to a position determined in advance for each of the corresponding external access ports. an endoscope having an insertion portion in which an observation optical system (31, 32, 33, 35) is provided; and a plurality of guide devices (3, 4) configured to be attached to external access ports different from each other of the engine and configured to guide the insertion portion of the endoscope into the engine, wherein each of the guide devices (3, 4) has: a guide tube configured to guide the insertion portion; a first fixing portion which is provided on the guide tube and is configured to fix the guide tube in the corresponding external access port; and a second fixing portion configured to fix the insertion portion in an axial direction of the guide tube; and a rotational movement amount restricting mechanism portion (21a,21b,25A,81a,81b) which is provided in the guide tube and is configured to restrict a rotational movement amount of the insertion portion around the axial direction of the guide tube, wherein a guide tube configured to guide the insertion portion; a first fixing portion which is provided on the guide tube and is configured to fix the guide tube in the corresponding external access port; and a second fixing portion configured to fix the insertion portion in an axial direction of the guide tube; and a rotational movement amount restricting mechanism portion (21a,21b,25A,81a,81b) which is provided in the guide tube and is configured to restrict a rotational movement amount of the insertion portion around the axial direction of the guide tube, wherein a length (L1,L2) of an extending portion of the guide device (3, 4), which is configured to extend from the corresponding external access port, is different among the plurality of guide devices (3, 4) so that, when the insertion portion is attached to the second fixing portion, a position for observing a predetermined portion of the blade by the observation optical system (31, 32, 33, 35) of the insertion portion comes to a position determined in advance for each of the corresponding external access ports.