It is an object to provide a boarding bridge in which differences in level are eliminated between walkway portions of adjacent gangway units so that falling or the like of passengers can be prevented. A boarding bridge is provided in which a proximal-end tunnel and a distal-end tunnel are telescopically fitted and extend and contract by relative movement in a longitudinal direction, wherein, of the proximal-end tunnel and the distal-end tunnel, a variable-length walkway of the distal-end tunnel located on the outside is configured to move between a passage position set at a predetermined height and an outside-of-passage position located lower than the passage position; and the longitudinal length of the passage portion is changed in accordance with a moving distance along with the movement relative to the proximal-end tunnel.