The pulley device for a tensioner roller or an idler roller of a transmission element having a pulley and a bearing. The bearing is provided with a rotating external ring mounted to the pulley, and with a fixed internal ring, a radial space being defined between the rings, with rear sealing means and front sealing means closing the radial space on each axial side, and with at least one row of rotating elements arranged in the radial space. The fixed internal ring is provided on its rear side with a circumferential groove for collecting pollution which is machined on an external surface of the ring, the circumferential groove being offset axially in relation to the rear sealing means outside the radial space.