Abstract: Disclosed is a mechanism for automatically changing closestool seat sanitary cover mainly includes a roll-up mechanism and a specially designed closestool seat. The roll-up mechanism includes a supply reel on which continuous sleeve-like sanitary cover is wound, an upper and a lower reels for pulling used sanitary cover away from the closestool seat, and a motor for rotating the upper and the lower reels in opposite directions. The closestool seat is substantially a C-shaped member having two end portions separately pointing to the supply reel and to the upper and the lower reels.