The optical transparency of poly(lactic acid) PLA films containing a specific nucleating agent, i.e., N,N’-ethylenebis(12-hydroxystearamide) (EBHS), was studied. Exposure to annealing treatment beyond the glass transition temperature was found to be significantly effective to increase the crystallinity without losing the transparency of quenched films. The annealed film showed a good heat resistance due to high crystallinity. EBHS was well dispersed in the molten PLA and formed network structure. As a result, crystalline size of PLA was reduced without spherulite texture, leading to a low level of light scattering.