Abstract: The present invention provides a novel adsorbent carbon, water quality purifier, water quality purifying bag and water quality purifying substrate which are floated on the water for a long time when sprayed, and as a result, are in contact with oil (oil film) contained in, particularly, natural waters such as rivers, lakes and the sea, waste water such as effluents from factories, sewage, basins of rain water and are present in a floated state on the water, to thereby remove the oil (oil film) in an efficient manner, and a method of removing an oil film. The adsorbent carbon is formed by using a coconut mesocarp as its raw material and by carrying out heating and carbonizing treatment of the mesocarp.