A sliding door may include a rail slidably supported by a rail anchor, a body part fixed to the rail, a main arm hinge-connected with the body part, a driving bar hinge-connected with the body part, a first link hinge-connected with the main arm and the driving bar, a second link hinge-connected with the main arm and a first slot of the driving bar, a door part hinge-connected with the main arm and having a second slot hinge-connected with the second link through the first slot, a gear part of the main bar, a first drum engaged to the gear part, a first cable connected with the first drum and the rail anchor, a second drum rotatably mounted at the rail, a second cable wound around the second drum and connected with the first drum, and a third cable connected with the second drum and the rail anchor.