Three dimensional residual stress distributions in a 4 inch diameter carbon steel pipe welded joint were measured by neutron diffraction technique. The results showed that the residual stress distributed near the weld metal, namely within about 30mm. The major tensile stresses occurred in the hoop direction in the fusion and heat affected zones of the weldment, and they attained a level greater than 200MPa throughout the pipe wall thickness. While the axial residual stress at the inside surface was 40MPa, the stress at the outside surface was -100MPa. These residual stress distributions were compared with those measured by the X-ray diffraction techinique and strain gauge method, and they agreed with each other.