To eliminate a trouble, e.g. jamming or overload, in the incidental facility subsequent to a product carrying line by controlling the quantity of product to be dried at a specified constant level.

The dryer comprises a direct burning continuous dryer 2, a feeder 3 for throwing a material to be dried into a dryer 2, a combustor 7 for supplying hot air to the dryer 2, and a product carrier 10 disposed at the product outlet of the dryer 2 where the product carrier 10 is provided with a unit 11 for measuring the quantity of product continuously. The quantity of product measured by the unit 11 is compared with a preset quantity and the quantity of product to be dried is controlled to match both quantities.