To realize a highly accurate noncontact measurement of a specified semiconductor composition in a short time by estimating the composition of a specified semiconductor layer based on the peak wavelength of photoluminescence measurement of a compound semiconductor epitaxial wafer and then selecting only the compositions falling within a specified range.

An InGaAs layer has an energy gap dependent on the composition ratio of In (or Ga). More specifically, the energy gap decreases as the composition ratio of In increases and the peak wavelength of luminescence is varied as the composition ratio of In is varied. Photoluminescence is then measured for a compound semiconductor epitaxial wafer and the peak wavelength thereof is detected. Subsequently, the composition of In in the InGaAs layer is estimated and only such compositions as falling within a specified range are selected thus realizing a highly accurate noncontact measurement of the composition of In in the InGaAs layer of a semiconductor epitaxial wafer in a short time.