A plurality of seed crystal films of a single crystal of a nitride of a metal belonging to group III are formed on a substrate, while a non-growth surface not covered with the seed crystal films is formed on the substrate. A single crystal of a nitride of a metal belonging to group III is grown on the seed crystal film. A plurality of the seed crystal films are separated by the non-growth surface and arranged in at least two directions X and Y. The maximum inscribed circle diameter “A” of the seed crystal film is 50 μm or more and 6 mm or less, a circumscribed circle diameter “B” of the seed crystal film is 50 μm or more and 10 mm or less, and the maximum inscribed circle diameter “C” of the non-growth surface 1b is 100 μm or more and 1 mm or less.