Recently poly(L-lactide) synthesized from starch is attracting much attention as a biodegradable polymer. In this paper, effects of crystallinity on dielectric properties of PLLA were studied by preparing four kinds of PLLA samples with different crystallinities. A thermally stimulated polarization current (TSPC) peak was found to appear in all the samples at temperatures around 65 to 70 °C, which is due to the glass transition. The magnitude of the TSPC peak was found to be in the reverse order of crystallinity. This is presumably because the segmental-mo de relaxation, which brings about the TSPC, is restricted more as the crystallinity increases. All the samples show two thermally stimulated depolarization current (TSDC) peaks at around 65 °C and around 90 to 100 °C. The lower-temperature peak seems to be due to the segmental-mode relaxation, while the other due to the normal-mode relaxation. Moreover, all the samples show a drastic increase in the real part of complex permittivity and have a peak in its imaginary part at frequencies from 10 -1 to 104 Hz, depending on the measurement temperature. The crystallinity dependencies of the two parts are similar to those of the TSPC and TSDC peaks around 65 to 70 °C. Therefore, the increase in the real part and the peak in the imaginary part are ascribable to the segmental-mode relaxation.