In this study, rheological properties of cement pastes containing ground Finex-slag (4000, 6000, 7000 c$m^2$/g) were investigated bymini-flow test and coaxial cylinder viscometer. And also blast furnace slag(4000, 6000, 7000 c$m^2$/g) were used for comparison. According to the experimental results, Finex-slag and blast furnace slag showed very similar trend in the rheological properties of the cement pastes. The fluidity of cement pastes blended Finex-slag and blast furnace slag powder were improved by high replacement ratio. In the relationship of plastic viscosity and yield stress appeared the tendency of the proportion greatly. And in the relationship of plastic viscosity, yield stress and mini-flow appeared the tendency of the inverse proportion.