Abstract: A rolling bearing unit with seal device comprises an outer ring member having an inner peripheral surface formed with outer ring raceways in double rows, an inner ring assembly having an outer peripheral surface formed with inner ring raceways in double rows opposed to the outer ring raceways and having an outward flange projected from the open end portion of the outer ring member, a plurality of rolling elements provided between the outer ring raceways and the inner ring raceways, respectively, and a seal ring for covering an annular space between the outer ring member and the inner ring assembly and comprising a reinforcing metal, a first side seal lip on the radially outer side having a tip edge in sliding contact relation with a side face of the outward flange, a second side seal lip on the radially inner side having a tip edge in sliding contact relation with a tip edge in sliding contact with a curved surface portion through which the side face is continued to the outer peripheral surface of the inner r