Disclosed is a thermally assisted magnetic recording medium comprising a substrate, a plurality of underlayers formed on the substrate, and a magnetic layer which is formed on the underlayers and predominantly comprised of an alloy having an L10 structure, characterized in that at least one of said underlayers is predominantly comprised of MgO and comprises at least one kind of an element having a free energy for oxidation of, per mol of oxygen, not higher than −120 kcal/mol·O2 at 1000° C. The element having the free energy for oxidation is preferably selected from Al, Si, Ti, V, Cr, Mn, Zr and B. The thermally assisted magnetic recording medium has a magnetic layer comprised of magnetic crystal grains with uniform diameters, and exhibiting a sufficiently weak exchange coupling between magnetic grains.