An air-bearing center-guiding apparatus is disclosed for supporting and laterally center-guiding thin, flexible webs of paper or plastic under 15 mils in thickness. The apparatus comprises a web support and guide member 10 having an inner surface 58 and an outer web-facing surface 60. The web support and guide member 10 comprises a base member 14 for supporting an inner ring 22, an end cap 38, and a center ring 28 interposed therebetween. Parallel, circumferentially extending rows of circumferentially elongated and spaced-apart guide apertures 62 are provided in the web support and guide member 10 along edge regions of the web. The guide apertures 62 are formed between end surfaces 46 of the center ring 28 and interengaging end surfaces of the inner ring 22 and end cap rings 38. Each guide aperture 62 extends substantially perpendicular to the surface of the web and defines in cross-section an opening having a straight side and a curved side for directing jets of air against the web edges for developing a guiding force for holding lateral movement of the web to plus or minus 0.001 inch (0.0254 mm). A row of support apertures 56, separate from the guide apertures 62, is provided in the center ring 28 between the rows of guide apertures 62 to form an air-bearing for the web.