To efficiently perform build-up welding for imparting high abrasion resistance to a long screw conveyor inside a common building with usual height.

The screw conveyor 1 is set such that the screw shaft 2 becomes almost horizontal, and while rotating the screw conveyor 1 around the screw shaft 2, the abrasion resistant build-up arc welding is applied on the blade side face 4 directing the torch tip 22 of a welding torch 21 toward the horizontally sideways direction to the blade side face 4 of the screw blade 3 of the screw-conveyor 1. The welding is performed using a welding wire 23 of 1.2-1.6 mm in diameter at the heat input of 2-9 KJ/cm.