To provide an improved apparatus for manufacturing composted materials capable of efficiently composting wastes without preliminarily carrying out delicate adjusting of water content.

This apparatus for producing composted materials is provided by improving an apparatus equipped with a processing cylinder 1 having an input port 2 for materials to be treated on one end, while an discharge port 3 of the treated material on the other end, a rotation shaft 4 extending in the inside of the processing cylinder from the aforesaid input port toward the discharge port, a screw transport means 6 installed on the outer periphery of the rotation shaft located in the vicinity of the input port and transporting the material to be treated put into the treating cylinder from the input port toward the discharge port, a frictional kneading means 7 installed on the outer periphery of the rotation shaft located on the downstream of the screw transport means, cutting the material to be treated with resisting against the transporting force of the screw transport means and raising temperature of the materials to be treated by frictionally kneading and comprising several rotative blades and a gate material 3a. In this invention the rotation shaft is formed to have a larger shaft diameter from upstream to downstream direction and the treating cylinder has a water drainage means 17 on its bottom.