Luminescence efficiency of InxGa1-xN-based light-emitting diodes (LEDs) has been studied by means of excitation-power-density- and temperature-dependent photoluminescence spectroscopy. The internal quantum efficiency (IQE) of LEDs was evaluated at various excitation photon energies using a wavelength-tunable dye laser system. The IQE obtained under selective excitation of InxGa1-xN active layers was approximately 1.5 times as high as that obtained under band-to-band excitation of GaN and AlGaN cladding layers.