PURPOSE: To improve the easiness, economy and productivity in producing ≥2 kinds of cements having a different composition by crushing and classifying a clinker of single composition.

CONSTITUTION: Clinker and gypsum are supplied to a mill 3 respectively from a clinker silo 1 and a gypsum silo 2 and crushed at the same time. The crushed material is charged into a cyclone separator 5 through a bucket elevator 4 and preclassified into the coarse grain and small grain. The coarse grain is returned to the mill 3 through a return line 6, the small grain is air-floated into a small cyclone 7 and classified into the fine powder and fine grain, the fine powder is discharged from a discharge line 8 as product I. Meanwhile, the fine powder entrained by a gas and discharged from the cyclone 7 is collected in a bag filter 9 and discharged from an outlet 10 as product II. Product I is relatively rich in C2S and C3A and product II in C3S and C4AF, and a cement of desired composition is produced by mixing both products in a specified ratio.