To provide a clinker adhesion preventing agent which is added to a combustion furnace or exhaust gas from the combustion furnace, and effectively exerts a clinker adhesion preventing or suppressing effect.

The clinker adhesion preventing agent is added to a combustion furnace or exhaust gas from the combustion furnace to prevent adhesion of clinker, and it is a clinker adhesion preventing agent including a magnesium compound, and has a bulk density of 0.1-0.9 g/ml and an average particle size d50 of 1-20 μm in JIS R 1628. A higher clinker adhesion preventing or suppressing effect by a lesser addition amount than conventional can be provided by a yield improvement effect to the clinker while being the proper particle size, and a superior sintering delay effect of the clinker while being the proper bulk density.