To efficiently mill cement clinker and improve characteristic of produced cement by adding a styrene-maleic acid anhydride copolymer superplasticizer to a cement clinker-milling auxiliary.

This cement-milling auxiliary is obtained by adding a styrene- maleic acid copolymer superplasticizer represented by formula I [R is a 2-6C alkylene group; R1 is a 1-20C alkyl or a 6-9C cycloalkyl or phenyl group; (x), (y) and (z) are each 0.01-100; (m) is 1-100 and (n) is 10-100, with the proviso that (x) to (y+z) is (1:10) to (10:1); (z) to (y) is (3:1) to (100:1); (m+n)=15-100] or formula II (M is hydrogen or a hydrophobic polyalkylene glycol residue of polysiloxane) to a cement-milling auxiliary. The clinker-milling auxiliary is added before or during milling of cement clinker. An amount of the auxiliary added is about 0.05-1.0% based on cement clinker.