PURPOSE: To improve the air-tightness of a sliding door device by fitting a ball caster of a panel to a drawing groove inclined to a meeting style side for a travelling groove before a sliding door panel is closed, and moving the panel to the meeting style side to pull it near to the meeting style side.

CONSTITUTION: In directly before the closing position of a sliding door panel 4, a ball caster 11 provided to the lower end of the panel 4 is fitted into a drawing groove 15 extended slantly backward from a travelling groove 9 provided on the surface of a doorsill. After that, the caster 11 is moved slantly backward through a groove 15, so that the panel 4 is pulled near to a slantly backward meeting style side. Then, the meeting style surface of the panel 4 is fixed through a packing and is pushed against the meeting style surface of a panel 4, and a space between the meeting style sections is surely sealed. By the constitution, excellent air-tightness can be ensured and, at the same time, cost can be reduced.