This invention provides a technique for rendering bio-toxicity such as allergy toxicity derived from Ni trace impurity, i.e., nickel toxicity, which is unavoidably present in a bio-Co-Cr-Mo alloy or an Ni-free stainless steel alloy unharmful, characterized in that an element selected from the group consisting of the group 4, 5 and 13 elements of the periodic table, particularly an element selected from the group consisting of the group 4 elements of the periodic table, is added to the alloy composition. The additive element is preferably an element selected from the group consisting of zirconium and titanium, more preferably zirconium.
