To arrange a drain port close to the rear end of the upper opening of a bowl or on the deeper side over it to create the depth feeling when the bowl is seen from above by making the rear wall part of the bowl into an inclined surface as it is situated backward toward the lower part, and providing the drain port on the bottom of the rear part of the bowl.

This rear wall part 4 of a bowl 2 is made into an inclined surface 5 as it is situated backward toward the lower part, and a drain port 1 is provided on the bottom of the rear part of the bowl 2, whereby the drain port 1 provided on the bottom of the rear part of the bowl 2 can be arranged close to the rear end part of the upper opening of the bowl 2 or on the deeper side over it, so that the depth feeling of the bowl 2 can be created when the bowl 2 is seen from above. Since the lower part of the rear wall part 4 of the bowl 2 is recessed toward the deeper side over the rear end of the upper opening of the bowl 2, the capacity of the bowl 2 can be increased. Further, the drain port 1 of the bowl 2 is shifted to the deep side, and a water pipe 8 is shifted to the deep side within a cabinet 7, whereby the housing space can be increased.