Microstructural characteristics of friction-stir-welded Al 6061-T651 with varying rotating and advancing speed were examined by the electron backscattering diffraction (EBSD) installed in field emission-scanning electron microscopy (FE-SEM). It was found that FSW produced an equiaxed fine-grained microstructure in weld zone and the grain size in weld zone decreased up to about 4 similar to 6 mu m with decreasing rotating speed. The primary textures developed in weld zone were {100}< 001 >, {110}< 001 > and {111)< 110 >. In thermo-mechanical affected zone, the change in grain size was not significant, however, large number of low angle grain boundaries were observed, which seems to be concerned with the formation of subgrains due to the development of dislocation cells.