To provide a kneading screw which has high hardness and excellent wear resistance and corrosion resistance, particularly is resist resist to stress corrosion cracking, and can be obtained using an in expensive material.

The kneading screw is composed of high-silicon stainless steel containing, by weight, 3 to 5% Si, 0.5 to 1.5% Mn, 0.8 to 1.2% Cu, 6 to 7% Ni, 10 to 13% Cr, 0.3 to 1% Mo, 0.3 to 1% Nb and ≤0.02% C and also containing, as impurities, ≤0.04% P and ≤0.03% S in Fe.