A gallium nitride substrate includes a plurality of physical level differences in a surface thereof. All the physical level differences existing in the surface have a dimension of not more than 4 μm. A relationship of (H−L)/H×100≦80 is satisfied in all the physical level differences, where H represents a higher value of cathodoluminescence emission intensities of a wavelength corresponding to a bandgap of the gallium nitride substrate, and L represents a lower value of the cathodoluminescence emission intensities, the cathodoluminescence emission intensities being measured in an upper step and a lower step of the physical level difference.