To drain as smoothly as possible on washing of a pan or the like.

If the upper surface of the rear part 17b of a lid body 17 is flush with the upper surface of the bottom wall 7 of a sink 3, drain is not carried to a drain port 19 when the drain port 19 formed in the rear part 17a of the lid 17 (whose area is smaller than that of the rear part 17b of the lid body 17) is perfectly covered with the bottom wall of a pan. However, even if the drain port 19 is perfectly covered with the bottom wall of the pan, the drain can be carried to the drain port 19 unless the rear part 17a of the lid body 11 is perfectly covered.