The molecular and lamellar orientations of injection-moulded isotactic polypropylene were investigated using simultaneous wide- and small-angle X-ray scatterings. In order to obtain the meaningful degree of molecular orientation with respect to the flow direction, the axis orientations of parent and daughter lamellae were separately calculated. The molecular orientation of thin material is consistent with the lamellar orientation. However, the decrease in the lamellar orientation of thick material is associated with a constant degree of molecular orientation, which would indicate an intra slip between parent lamellae along the flow direction.