A threshing device includes a threshing part with a rotatable unit which includes at least a flail and a concave which surrounds the rotatable unit. The concave is rotatably arranged in an opposite direction in relation to the rotatable unit. The threshing device includes a cleaning part with a rotatably mounted sieve, which surrounds the concave. A fan is arranged to provide an air stream towards the sieve for preventing the cleaned parts of the threshed material to pass through the sieve. The air stream is also arranged to transport out the cleaned parts which are collected in a space between the sieve and the concave.
