On an RAMO4 substrate containing a single crystal represented by the general formula RAMO4 (wherein R represents one or a plurality of trivalent elements selected from a group of elements including: Sc, In, Y, and a lanthanoid element, A represents one or a plurality of trivalent elements selected from a group of elements including: Fe(III), Ga, and Al, and M represents one or a plurality of divalent elements selected from a group of elements including: Mg, Mn, Fe(II), Co, Cu, Zn, and Cd), a buffer layer containing a nitride of In and a Group III element except for In is formed, and a Group III nitride crystal is formed on the buffer layer.