A rotary dryer, wherein a mechanism having a discharging action in reverse rotation is provided inside a drying drum and the drying drum is rotated reversely in a process where drying substance is discharged, and also the dried object and drying substance are prevented from being dispersed at the time of charging and discharging them, a plurality of the drums are provided continuously and a specified relation is given between the rotating direction, time, and speed of each drum so as to reduce an operational play of each drum in order to increase the efficiency of the entire dryer.