A top-down bottom-up window covering includes a first beam and a second beam, which are sequentially provided below a fixture, and a covering material connecting the first beam and the second beam. A first lifting structure is installed in the first beam, and a second lifting structure is installed in the second beam. The first lifting structure is adapted to operate as the first beam is being controlled to move toward or away from the fixture, and the second lifting structure is adapted to operate as the second beam is being controlled to move toward or away from the fixture. Thus, the top-down bottom-up window covering can be easily assembled and maintained.