The time-differential perturbed angular correlation method with the ¹⁴⁰Ce probe was applied to a microscopic investigation on a perovskite manganite, La_0.7Ca_0.3MnO₃. A drastic change was observed in the time evolution of the directional anisotropies around the Curie temperature (T_c∼245K), reflecting the paramagnetic-ferromagnetic phase transition. The internal magnetic field at the probe nucleus stabilized at the A site was estimated to be B_int=6.9±0.3T at 240K, whereas no appreciable magnetic field was observed at 260 K. From a comparative study using two different probe-introduction methods, in addition, we found that ascendant ions of the probe, ¹⁴⁰Ba and ¹⁴⁰La, can be located at the A site by heat treatment.