To provide a screw conveyor formed by two-direction split dies.

In the screw conveyor 10 with screw blades 2 spirally disposed around a rotary shaft 1, a vertical separating line A-B is assumed in the axis. A thickened portion 21 is formed from a blade top portion 23 to the vertically separating line A-B so as not to generate an undercut in the screw blades. A counter side 22 is also formed corresponding thereto. As shown in the figure, the thickened portion 21 and the counter side 22 are opposite to each other vertically in the right-to-left direction. Since no undercut is formed in the screw blades 2, a die can be vertically split even when two-direction separation dies are used. The two-direction dies can be used in the manufacture, and the manufacturing cost including the cost of the dies can be considerably reduced.