PURPOSE: To prevent the infiltration of incontinent excreta into a bed and improve the deodorization, sterilization, and electrification effect by using a waterproof, moisture-permeable sheet made of a porous film partially stuck with protective fabric at least on one face as a cover sheet, and fitting a gas exhaust filter at the side wall upper end section of a bed vessel.

CONSTITUTION: The upper face of a porous film 1 is covered with a hydrophilic resin layer 2, and protective fabric 3a is provided on it. A protective fabric 3b is provided below the porous film 1 to form a soft, waterproof, moisture- permeable sheet A. A deodorant and an antibacterial agent are contained in the resin layer 2, and the deodorant and the antibacterial agent are also contained in the protective fabric 3a. The protective fabric 3a is woven with conducting fibers containing an electrification preventing agent. An air filter 9 is provided at the side face upper section of a chamber B, and the gas fed to the chamber B from a chamber C by a pump is discharged to the outside via the air filter 9 without passing through the sheet A.