PURPOSE: To obtain a solid fuel which is easy to handle, excellent in ignitability and large in calorific value and emits no harmful substances, by forming a plastic film on the surface of an org. granule obtd. by hardening an industrial waste comprising a combustible organic matter with a sizing agent.

CONSTITUTION: An industrial waste comprising a combustible organic matter such as paper sludge or waste food is sufficiently dried and pulverized to obtain an org. matter powder. The org. matter powder is sprayed with a liq. sizing agent (e.g.: starch) or immersed in a liq. sizing agent and hardened into a granule 1 having a desired size. The org. matter granule 1 is sprayed with a soln. contg. a waste plastic dissolved therein or immersed in the soln. contg. a waste plastic dissolved therein, and the solvent is volatilized to form a plastic film 2 on the surface of the org. matter granule 1.