Optical transmission spectra of CuCl microcrystals embedded in NaCl crystals were studied around theZ3exciton resonance by varying the annealing time. With the increase in the annealing time, extinction spectra of theZ3exciton change anomalously from the absorption‐type spectrum to the emission‐type spectrum via the dispersion‐type spectrum. The Mie theory [Ann. Phys.25, 377 (1908)] successfully explains the spectral change due to the growth of microcrystals. We report here for the first time an anomalous change of the exciton spectra due to the growth of semiconductor microcrystals.