A passenger boarding bridge comprises a first walkway of an inner tunnel of adjacent tunnels of an extendable and retractable tunnel section; and a second walkway of an outer tunnel of the adjacent tunnels, the second walkway including a plurality of floor members which are arranged in the front-rear direction and are coupled to each other. The plurality of floor members are supported by an endless string-shaped member that is rotatable. A respective walkway surface of each walkway is at a predetermined equal height position. When the tunnel section is retracted, the string-shaped member of the second walkway is guided so that the floor members are moved down to an underside of the inner tunnel, and when the tunnel section is extended, the string-shaped member of the second walkway is guided so that the floor members are moved up from the underside of the inner tunnel.