To improve durability of a seal lip (4) of an oil seal (1) in slidably contact with the peripheral surface of a shaft (23), a lubricating oil supply section (11) for collecting adhered oil and dropping it on the shaft (23) is provided at a forward end portion of an installation section (2), the lubricating oil supply section (11) has projections (12) formed on the inner peripheral surface of the installation section (2) to collect oil on the surface thereof, the surface of each projection (12) has a recess (13) for temporarily accumulating oil, guidance projections, or a slope for collecting the oil, and dams are formed on a forward end face (2a) of the installation section (2) to block the oil flowing down along the circumferential direction on the forward end face (2a) and guides the oil toward each projection (12).