[en] For the understanding of Ce-doped high-T_c cuprates with the so-called T'-structure, we have performed "6"3","6"5Cu and "1"3"9La NMR measurements in T'-Pr_1_._3_−_xLa_0_._7CexCuO_4_+_δ single crystals with x = 0.10 and 0.15. The Néel temperature (T_N) was evaluated from the temperature (T) dependence of the "1"3"9La NMR line width. For x = 0.10, T_N decreased from 190 K in the as-grown crystal to 60 K in the oxygen-reduced crystal annealed at 800°C. For x = 0.15, T_N of 170 K in the as-grown crystal decreased to zero through the same heat treatment. The oxygen reduction strongly suppressed the antiferromagnetic (AF) order. "6"3","6"5Cu NMR spectra had a narrow center line and broad satellites with a small electric field gradient in the paramagnetic state. In the AF state, in contrast, "6"3","6"5Cu NMR spectra had a large electric field gradient. The T dependence of the "6"3Cu nuclear spin-lattice relaxation rate (1/T_1) showed the existence of large spin fluctuations in the paramagnetic state. The spin fluctuations seem to play a key role in the appearance of superconductivity in the T'-cuprates. (author)