To provide a watertight protector for a diseased part which is easily and rapidly fitted on a body and prevents surely water such as hot water from penetrating.

A belt-like body 4 comprising a flexible closed cell foamed body is bonded along an opening edge part 2a of one end part of a bag-like body 2. A loop with a size being suitable for the diseased part is formed by laminating a specified range of this belt-like body 4 and the gap between a joint of this loop and the diseased part is closed by a tongue piece 5 projected on the inner periphery of the belt-like body 4. Specified parts of the outer peripheral side of the belt-like body 4 are hooked together by face fasteners 7 and 8 provided on the outer peripheral side of the belt-like body 4 so as not to make the above described loop come loose.