To provide a counter unit which makes the drainage equivalent to that in an under sink while the installation workability is identical to that in an over sink.

The counter unit is formed by including a sink S formed by integrally including, at an opening edge 1a of a sink body 1, a flange part 2 made of a metal plate projecting horizontally from the opening edge 1a to the outside and a top plate P including a receiving hole 3 receiving the sink body 1 of this sink S from above to hook the flange part 2 of this sink S to a hole edge 3a. The projecting end 2d of the flange part 2 of this sink S and the step 3b of the top plate P are matched without a gap, and the sink S and the top plate P are made to combine with each other by allowing the upper face 2a of the flange part 2 and the upper face 4 of the top plate P on the step 3b to be positioned on the same face.