PROBLEM TO BE SOLVED: To provide a processing method for granular powders capable of suppressing the initial moisture percentage of the granular powder before drying by suppressing the moisture absorption of the granular powder in a first storage tank.SOLUTION: A processing device 1 for granular powders has a first storage tank 10, a second storage tank 20 and a conveyance tube 30 connecting both storage tanks. Besides, the device 1 has a first gas introduction part 60 introducing an inert gas in the first storage tank 10 directly or through the conveyance tube 30. In processing the granular powder, firstly the gas in the first storage tank 10 is replaced with the inert gas and then, the granular powder is charged in the first storage tank 10. Thereby, the moisture absorption of the granular powder 9 in the first storage tank 10 is suppressed, and the initial moisture percentage of the granular powder 9 before drying is restrained. As a result, it becomes possible to lower the moisture percentage of the granu
