A roll shaft structure is provided for fixing a first roll or a second roll. The roll shaft structure includes a shaft body, a first ring and a second ring. The diameter of the shaft body is equal to the inner diameter of the first roll. The diameter of each of the first ring and the second ring is equal to the inner diameter of the second roll. When the shaft body penetrates through the first roll, the shaft body is contacted with the inner wall of the first roll, so that the first roll is fixed on the roll shaft structure. Whereas, when the shaft body penetrates through the second roll, the first ring and the second ring that are fixed on the shaft body are contacted with the inner wall of the second roll, so that the second roll is fixed on the roll shaft structure.