In this paper, roughness profiles of a cylindrical workpiece and relative displacements between tool and workpiece are investigated in turning operations. The correlation between the roughness profile and relative displacement is observed at the same conditions. Especially, the surface profile of the circumferential direction of the finished workpiece as well as the radial motion of spindle is analyzed by means of Fourier transform. As the results, it is found that the roughness profile along the axial direction is not mainly influenced by the corner radius of the tool but by the radial motion of spindle, and its radial error motion decides the limiting surface roughness. In addition, the radial motion of spindle is precisely analyzed, and it is found that there are two types of radial error motions ; the radial movement of rolling elements of bearings of the spindle and natural frequency of the structure.