PURPOSE: To attain a uniform mixture by one stage by calculating the amount of residue beforehand on the basis of a weighed value of charged powder to be used and a weighed value of discharged powder after mixing and by determining the amount of powder to be charged, so that the total amount with the residual powder be a desired value.

CONSTITUTION: After the amounts of material powders A and B to be charged are calculated, weighing is conducted. Then, the powders A and B are charged in a ball mill and mixed. Next, the amount of residue is calculated beforehand on the basis of weighed values of the charged powders and a weighed value of discharged powder after the mixing. Next, the amount of powder to be charged is determined so that the total amount with the previous residual powder be a needed value. When a necessary constituent is changed, the amount of material powder to be charged can be determined so that the necessary constituent be attained, inclusive of the previous residual powder, by this method and, besides, necessary uniform powder can be obtained without producing a scrap and with a mixer of one stage employed.