PURPOSE: The titled machine, designed to set the rotational speed of a rotating drum according to the amount of a material to be dried, capable of preventing the material in a large amount from entangling in the form of a dumping and further the rotation of the material to be dried together with the drum while sticking to the inner surface thereof.

CONSTITUTION: A lead switch 12 is turned on by a permanent magnet 10 on every rotation of a rotating drum 1, and signals generated by the turning on of the lead switch 12 are processed by a control circuit to sense the rotational speed of the rotating drum 1. The control circuit is capable of keeping the output of a motor 3 at the time of starting the hot-air drying step constant, and sensing the amount of a material to be dried contained in the rotating drum 1 on the basis of the signals from a sensing mechanism 9 for the rotational speed to store the amount in a memory. Thus, the rotational speed of the motor 3 is changed in proportion to the memorized amount of the material to be dried.