A composite substrate for the formation of a light-emitting device, ensuring that a high-quality nitride-based light-emitting diode can be easily formed on its top surface and the obtained substrate-attached light-emitting diode functions as a light-emitting device capable of emitting light for an arbitrary color such as white, is provided. A composite substrate for the formation of a light-emitting device, comprising a light-converting material substrate for radiating at least a part of incident light as light different in the wavelength through the surface opposite the incident surface, and at least two or more Al-containing nitride layers formed on the light-converting material substrate, wherein the light-converting material substrate has a texture comprising two or more oxide phases continuously and three-dimensionally entangled with each other, including an Al2O3 phase and at least one fluorescence-emitting oxide phase, and the nitride layer has a first layer of an Al-containing nitride layer formed on the light-converting material substrate and a second layer of AlN having a dislocation density of 1×1012/cm2 or less and preferably having a surface roughness (RMS) of 10 nm or less.