To provide a sliding door apparatus which is of a relatively simple structure, and minimizes formation of a gap between a sliding door and a floor.

The sliding door apparatus is comprised of a sliding door main body 5, sash rollers 2, a protruding piece 1, and a first groove 4. The sash rollers 2 are attached to the lower bed of the sliding door main body 5. The protruding piece 1 is arranged on the lower bed of the door main body 5 over the almost entire length thereof in a manner protruding lower than a lower edge of each sash roller 2. The first groove 4 accommodates therein the entire lower portion of the protruding piece 5 in a slidable manner. The first groove 4 is formed in the floor 6 in a sliding direction of the sliding door main body 5 over a length corresponding to the sliding of the sliding door main body 5.