To reduce the concentration of phosphorus in coal without detriment to the caking property of coal and minimize the possibility of an increase in the discharge of chemical substances harmful to the environment during use by bringing coal into contact with an organic acid.

The organic acid used preferably comprises a liquid organic acid in particular. The liquid organic acid may be an organic acid that becomes liquid at the service temperature, or one dissolved in a solvent such as water to form a liquid. The organic acid preferably comprises one consisting of carbon, oxygen and hydrogen atoms, for example, oxalic acid, citric acid or formic acid. The liquid organic acid preferably has a pH of 3 or lower. Examples of the method for bringing coal into contact with the liquid organic acid include a batch processing method wherein coal is put in a water tank containing the liquid organic acid, a method of scattering the liquid organic acid on coal, and a method of immersing coal in a circulating liquid comprising the liquid organic acid. The coal when brought into contact with the acid is preferably in powdery form, with a size of about 20-1 mm more preferably.