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.