Abstract: A composting device including a drum rotatably arranged about an axis slightly inclined to the horizontal, and having a feeding opening for composting material at the higher situated side of the drum and a discharge opening for finish composted material at the lower side of the drum, the interior of the drum being subdivided into a number of consecutive chambers arranged in the longitudinal direction of the drum, with intermediate sieve screens, whereby the adjacent chambers of the drum are entirely separated from each other by the sieve screens, whereby each sieve screen has the same size of meshes over its entire surface, and where each sieve screen has smaller mesh size in relation to the nearest preceding sieve screen.