A catheter includes a tubular catheter base having a single layer or a multiple-layer laminated base, wherein an innermost portion is made of ultrahigh molecular weight polyolefin. The layer of ultrahigh molecular weight polyolefin has a drawn region which has been drawn in the presence of a supercritical fluid in at least a longitudinal portion, and the catheter base possesses a densified region at the inner circumferential surface in at least the drawn region.
