Abstract: Ultrafine powder is stored in a pneumatic transportation tank (20), and is discharged to a transporting conduit (23) while being fluidized by the pressurized air fed through a fluidizing air port (24). The ultrafine powder is fed to a weigher (30) provided at the other end of the transporting conduit (23), at which the weight of the transported ultrafine powder is weighed by a load cell (31). After the weighed value reaches 90% of a predetermined value, the fed amount of the pneumatic transportation air is reduced, and a bypass regulating valve (38) is adjusted to thus decelerate the transportation. When the weighed value reaches 100% of the predetermined value, the discharge of the ultrafine powder to the transporting conduit (23) is stopped. This method and the apparatus enable the storage, quantitative batch transportation, and automatic weighing of the ultrafine powder such as silica fume.