In order to examine the applicability of biodegradable polymers to the fields of electrical insulation, several dielectric properties of two typical biodegradable polymers, polylactic acid (PLA) and starch ester (SE), are examined. A fairly larger amount of space charge is accumulated in both polymers in comparison to low-density polyethylene (LDPE). This seems partly due to the presence of hydroxyl and carbonyl groups in these polymers. Permittivity and conductivity are higher in SE than PLA that has the values close to those of LDPE. The dielectric breakdown strength is lower in SE and is higher in PLA than LDPE. As for the resistance to photodegradation by ultraviolet photons, SE is stronger than PLA, although the two are much inferior to LDPE.