PURPOSE: To provide a hollow ceramic member for cleaning waste water which floats on water to be able to treat effectively pollutants near the surface of water.

CONSTITUTION: A hollow ceramic member 10 for cleaning waste water which floats on water to treat stains on a water surface or an oil film has the maximum width across corners of 1-5cm, an outside shape resistant to breakage, and a sealed hollow space part 12 adjusting the total specific gravity to be less than 1.0 and is made of a material having a good affinity with bacteria. The sealed hollow space 12 makes the ceramic member 10 float on waste water, for example, in a waste water treatment plant. By the cultivation of oil- assimilating bacteria on the ceramic member 10, an oil film on the surface of waste water can be removed efficiently.