Abstract: A cone-and-screw mixer for mixing powders, granulates or polydisperse granular materials having a conical vessel accommodating a screw simultaneously rotating about its own axis and around the axis of the vessel. The mixer is provided with an inlet opening located in a cover, a pipe fitting located in the bottom and an overflow opening located between the inlet opening and the upper flight end of the screw. The area of the overflow opening is preferably equal to that of the inlet opening, whereas the angle included between the vertical planes passing through the mixer axis and through the points being least distant from each other and located at the edges of the overflow and the inlet openings is not less than 0.35 rad.