In poly(epsilon caprolacton) (PCL)/poly(vinyl butyral) (PVB) blend which forms band spherulite, some straight lines along the radial direction of the spherulites are observed under polarized optical microscope (POM). By using microbeam scanning WAXS, we have investigated the handedness of lamella twisting on the left and fight sides of the straight line. As a result, we have observed that the manner of periodic change of 110 reflection in WAXS is reversed between left and right sides of the straight line with respect to the direction of the X-ray beam scanning. This result clearly shows that the straight line observed under POM is the boundary line of handedness in band spherulite, and further, that both handednesses co-exist within one spherulite. It also implies that the lamellae growing from one nucleus are twisted cooperatively only with neighboring lamellae but not with all lamellae in the spherulite of PCL/PVB. (C) 2004 Elsevier Ltd. All rights reserved.