Precipitation phenomena in an austenitic stainless steel, SUS316L cold-rolled with various reduction rates were studied by transmission electron microscopy and synchrotron radiation diffractmetry. After the aging at 573 K for 15000 h, two of precipitates were observed, which were identified as M7C3 and M23C6 by SR diffraction and electro diffraction measurements. The precipitates M7C3 were formed at both innergranular and grain boundary, while the precipitate M23C6 was formed at innergranular. The precipitation was promoted with increasing cold rolling reduction. Also segregation of phosphorous was detected along grain boundaries. Besides, the residual stresses were measured with side inclination method using a synchrotron radiation facility, SPring-8. The residual stresses were increased with increasing the cold rolling reduction rate.