A rotunda height adjusting device of a boarding bridge , comprising: an external column fixed to a ground and having an inner space formed therein; an internal column configured to fix a rotunda , and coupled so as to be slidable in the inner space to ascend and descend; at least one drive unit configured to allow the internal column to ascend and descend with respect to the external column , and provided so as to be exposed to an outside of the external column and the internal column; and a power unit configured to provide power to the drive unit and control the drive unit, wherein the at least one drive unit is disposed adjacent to a circumference of the external column and configured to allow a vertical operation, the inner space comprises a plurality of divided empty spaces in an outer part excluding a central part into which the internal column is to be inserted, and a plurality of rotating rollers to be in contact with the internal column is provided in the divided spaces, wherein the rotating rollers comprise: a first rotating roller provided in an upper side of the divided spaces oriented in a motion direction in which the internal column moves; and a second rotating roller provided below the first rotating roller in the divided spaces oriented in a motion direction in which the internal column moves. an external column fixed to a ground and having an inner space formed therein; an internal column configured to fix a rotunda , and coupled so as to be slidable in the inner space to ascend and descend; at least one drive unit configured to allow the internal column to ascend and descend with respect to the external column , and provided so as to be exposed to an outside of the external column and the internal column; and a power unit configured to provide power to the drive unit and control the drive unit, wherein the at least one drive unit is disposed adjacent to a circumference of the external column and configured to allow a vertical operation, the inner space comprises a plurality of divided empty spaces in an outer part excluding a central part into which the internal column is to be inserted, and a plurality of rotating rollers to be in contact with the internal column is provided in the divided spaces, wherein the rotating rollers comprise: a first rotating roller provided in an upper side of the divided spaces oriented in a motion direction in which the internal column moves; and a second rotating roller provided below the first rotating roller in the divided spaces oriented in a motion direction in which the internal column moves. wherein the at least one drive unit is disposed adjacent to a circumference of the external column and configured to allow a vertical operation, the inner space comprises a plurality of divided empty spaces in an outer part excluding a central part into which the internal column is to be inserted, and a plurality of rotating rollers to be in contact with the internal column is provided in the divided spaces, wherein the rotating rollers comprise: a first rotating roller provided in an upper side of the divided spaces oriented in a motion direction in which the internal column moves; and a second rotating roller provided below the first rotating roller in the divided spaces oriented in a motion direction in which the internal column moves. wherein the rotating rollers comprise: a first rotating roller provided in an upper side of the divided spaces oriented in a motion direction in which the internal column moves; and a second rotating roller provided below the first rotating roller in the divided spaces oriented in a motion direction in which the internal column moves. <EOS>