A gallium nitride substrate comprising a first main surface and a second main surface opposite thereto, wherein the first main surface is a non-polar or semi-polar plane, a dislocation density measured by a room-temperature cathode luminescence method in the first main surface is 1×104 cm−2 or less, and an averaged dislocation density measured by a room-temperature cathode luminescence method in an optional square region sizing 250 μm×250 μm in the first main plan is 1×106 cm−2 or less.