A slinger of an oil seal has a thread groove carrying out a pumping action toward a diametrically outer side in an external side end surface of a flange portion. A lip seal member has a main lip, a rubber-like elastic dust lip and a rubber-like elastic intermediate lip. The intermediate lip directs a lip end to a machine inner side, comes into close contact with the slinger over a whole periphery with the lip end, and has annular first projections and circumferentially partial second projections in a facing portion to the slinger. The first projection has a structure which makes dust hard to pass through to the lip end by forming a micro gap in relation to the slinger. The second projection has a structure which properly keeps the micro gap under generation of eccentricity in a rotary shaft by having a higher portion than the first projection.