To provide a high strength free cutting martensitic stainless steel for cold forging, capable of setting aging temp. at a value selected from a wide range of temps. from 450 to 640°C and exhibiting excellent delayed fracture characteristic.

This free cutting stainless steel can be obtained by subjecting a stainless steel, having an alloy composition consisting of, by weight, ≤0.020% (≤0.009%, if necessary) C, ≤1.0% Si, ≤1.5% Mn, ≤0.03% P, ≤0.03% S, 2.00-4.00% Cu, 3.50-7.00% Ni, 14.0-17.0% Cr, ≤1.50% Mo, ≤0.040% N, 0.05-0.40% Nb, 0.0010-0.0100% B, and the balance essentially Fe and satisfying the condition of Nb%<8(C%+N%), to aging treatment at 450-650°C.