To secure the barrier-free structure indoors by providing a flat floor without steps in a door device having a sash roller.

A door device is provided with a sash roller 8 in a lower end of a door. A floor surface 2 opposite to the center of a lower end face of a door 1 is formed a flat surface without steps. A narrow guide groove 3 is formed in the floor surface 2 parallel to the lower end face of the door 1, and a closed guide member 7 whose tip is inserted in the guide groove 3 is fitted to the lower end of the door 1. The width of the guide groove is preferably ≤7mm.