A cement manufacturing apparatus capable of increasing quantity of fly ash used in the apparatus while controlling unburned carbon content in cement within a permissible range. The cement manufacturing apparatus comprises a removal means for removing unburned carbon from gypsum, and a grinding means for grinding gypsum from which unburned carbon is removed by the removal means together with clinker to generate cement. With the apparatus, total unburned carbon content in cement can be reduced, and the quantity of fly ash used in the apparatus can be, increased by the reduced amount of unburned carbon. The removal means can remove unburned carbon contained in gypsum as well as unburned carbon contained in fly ash, and the grinding means may grind the fly ash from which unburned carbon is removed together with the gypsum, from which unburned carbon is removed, and clinker.