To prevent lumps of ultrafine powder from developing locally and increase a throughput of powdered stock per unit time of an extruder by a method wherein an accepting tank with agitating blades is provided between a powder cyclone and a bag filter and a powder silo so as to agitate and mix the ultrafine powder and a powder together.

In this feeding method of a powdered stock, an accepting tank 20 with agitating blades is provided between a powder cyclone 1 and a bag filter 10 and a powder silo 5 so as to uniformly mix an ultrafine powder and a powder in the accepting tank 20 with the agitating blades and then feed the resultant powder to the powder silo 5, resulting in increasing the amount of supply of the powdered stock to an extruder 6 more than heretofore.