Provided is a method and apparatus for measuring efficiency of an optical device. In the method, a power of emission light from the optical device is calculated by irradiating an excitation stimulus on the optical device. A power of a reference excitation stimulus at which a variation of recombination coefficients in a quantum well of the optical device with respect to a variation of carrier concentration in the quantum well of the optical device becomes minimum is extracted. An internal quantum efficiency of the optical device at the power of the reference excitation stimulus is calculated. An internal quantum efficiency of the optical device at powers of various excitation stimuli is calculated from the internal quantum efficiency of the optical device at the power of the reference excitation stimulus.