A shaft structure includes a carrier, a first mandrel, and a second mandrel. The carrier has a groove, a receiving space communicated with the groove, and two protruding portions. The two protruding portions protrude from an inner wall of the carrier, and the two protruding portions are located between the receiving space and the groove. The first mandrel has a first gear, a first rotation shaft, and a first connection shaft connected to the first gear and the first rotation shaft. The first gear is located in the receiving space. The second mandrel has a second gear, a second rotation shaft, and a second connection shaft connected to the second gear and the second rotation shaft. The second gear is configured to move in the receiving space and the groove.