PURPOSE: To provide a soft magnetic alloy having high magnetic permeability and high heat resistance while it has sufficient saturation magnetic flux density equal to that of ferrite.

CONSTITUTION: The compsn. of the soft magnetic alloy is regulated to a one shown by CoxTayHfz wherein the relationship in the compositional ratios (x), (y) and (z) are regulated, by atomic%, to 78<x≤81, 8<y<15, 5<z<13, 1<y/Z<2.5 and x+y+z=100. The alloy is a one having extremely high magnetic permeability and in which magnetostriction is approximately close to zero and heat resistance is extremely high while it has saturation density equal to that of ferrite. Thus, a magnetic head excellent in magnetic properties can be produced.