The sliding door adopts of the design of special roller shaft, where the force on every hinge is distributed to the roller at both sides, therefore the door can slide mildly and the pulley’s service life can be extended. The door plank is made from two layers of electroplated steel plate inside and outside and the high-density polyurethane foaming material, and its surface can be cleaned easily. The door can be provided by multiple plank materials so as to adapt to the construction needs.