A method for observing the branch portion of the hole include: a step of pushing an obstacle in the hole aside with an elbow portion； a step of rotating a guide member around an axial direction so that a distal portion faces the branch portion extending laterally to an extending direction of the hole； a step of rotating an image to match an up-and-down direction of the image with an up-and-down of a vertical direction, at about the same timing as a timing to rotate the guide member around the axial direction； and a step of projecting an endoscope from the distal portion and inserting into the branch portion while confirming the image.
