PURPOSE: To achieve a good drying of granular material by rotating a drum so that the granular material enters from the front end of an immersion body and passes through the tunnel-formed interior of the immersion body and supplying a gas to and removing the gas from the interior of the immersion body through an opening for introducing and an opening for feeding out the gas in the interior of the immersion body.

CONSTITUTION: The immersion body 46 is arranged so that the body can immerse into the granular material 44 in the drum 10 having a shell 12 and a pair of end wall parts 14 being disposed apart in the direction of an axis line in the vicinity of both ends of the shell 12 and capable of rotating around the axis line. The granular material 44 is treated with a treatment device in which the interior of the immersion body 46 is constituted to the tunnel form so as to allow the annular material 44 to flow. At this time, the drum 10 is rotated so that the granular material 44 enters from the front end of the immersion body 46 and passes through the tunnel-formed interior of the immersion body. Then, the gas is supplied to and is removed from the interior of the immersion body 46 through plural introducing-openings 70 and feeding out-openings 72 for the gas in the interior of the immersion body 46. Consequently, the gas for drying the granular material and a material to be adhered to the granular material are utilized furthermore well.