To achieve a small magnetostriction and a large relative corrosion resistance in an amorphous magnetic alloy, by adding Rh to an amorphous composition containing an amorphous alloy having a general Co group as its main component, i.e., to the amorphous composition which contains Co and Fe of a specific percentage and the remaining portion is comprised of Zr, Ta, Nb, Hf, Ti and B.

A highly corrosion resistant amorphous magnetic alloy comprises Ta containing at least Fe and Co of (a) atomic %, Tb containing Rh of (b) atomic %, and Tc containing Zr of (c) atomic %. In this amorphous magnetic alloy, a, b and c satisfy the relations of 75≤a≥98, 2≤b≥20, and 2≤c≥15, and the total atomic % of the selected elements amounts to 100%, and its saturated magnetic flux density Bs is at least 12,000 gauss, and its saturated magnetostrictive constant λs is smaller than 1.0×10-6. The addition of Rf to such an amorphous alloy having a Co group is effective in the reduction of the corrosion rate of the amorphous alloy having a Co group.