PURPOSE: To discharge bulk material from an outlet uniformly with respect to the time and space, by providing the end section of a screw with a buffering section including a bladeless section and an auxiliary blade section having a plurality of blades.

CONSTITUTION: The screw 8 includes a screw main body 9 that comprises a screw shaft 1 having a shaft diameter (d) and blades 2 having a diameter (D) and a pitch (P) and the buffering section 13 at the end. The buffering section 13 has a blade decreasing section 10, the bladeless section 11 and the auxiliary section 12. As the bladeless section 11 is provided, the material around it will not be propelled axially and not be swirled, but dwells there, and therefore the uneven distribution of the material in a transverse direction and the fluctuation of the amount to be discharged can be relieved so that uniform discharge with respect to the time and space can be effected. Since the end of the bladeless section 11 has the auxiliary blade section 12 having the plurality of blades, the material filled and stored around the bladeless section 11 can positively be discharged.