To develop a novel structure for stirring/transporting a material to be treated in a rotary drum type dryer in which low quality refuse having a high moisture content can be reformed and drying efficiency of low quality refuse can be enhanced.

In the rotary drum type dryer, a matter to be treated supplied from the throw-in opening 20 of a rotary drum 2 is stirred by rotating the rotary drum 2 and blades 32 provided on a rotary shaft 30 disposed in the rotary drum 2, and dried by touching hot air. Then the dried matter is discharged sequentially from a discharge opening 21, spiral blades 31 are formed on the rotary shaft 30, and the matter to be treated having a lowered moisture content is mixed with a matter to be treated just thrown in by transporting the matter to be treated having a lowered moisture content to the throw-in opening 20 side by means of the spiral blades 31, thus lowering the moisture content of the matter to be treated located in the vicinity of the throw-in opening 20.