The invention relates to a mixer device for materials, i.e. materials made up of various divided solid waste, in a vertical silo (1). Said device is characterized in that it comprises the following: a central working area extending along the entire height of the silo (1); a peripheral zone; means (6) which are distributed vertically at different successive levels (n1, n2, n3 ... n21) of the working area, along the entire height of the silo (1) and which can lift materials from each of the levels of the working area and release said materials; means (la, 19) for bringing matter from the upper part of the peripheral area to the lower center part of the silo (1).