A rolling bearing with seal ring, comprising: an outer ring provided with an outer ring raceway around an inner-circumferential surface thereof; an inner ring provided with an inner ring raceway around an outer-circumferential surface thereof, having one end surface that is a flat surface with which a positioning member for regulating the position in the axial direction of the inner ring comes in contact, and located on an inner-diameter side of the outer ring so as to be concentric with the outer ring; a plurality of rolling bodies located in an internal bearing space that is formed between the outer ring and the inner ring, and arranged between the inner ring raceway and the outer ring raceway so as to be able to roll freely; and a seal ring fastened to one end portion of the outer ring; characterized in that the one end surface of the inner ring is located at a position further recessed in the axial direction than one end surface of the outer ring, the seal ring has a circular ring shape and comprises: an elastic member made of an elastic material and having a seal lip provided with a tip-end edge that comes in sliding contact with the one end surface of the inner ring; and a circular ring-shaped metal core reinforcing the elastic member, the inner diameter of the metal core is larger than the outer diameter of the inner ring, and the inner ring raceway of the inner ring is composed of a deep-groove inner ring raceway, and the diameter (D 23) of the sliding contact portion between the tip-end edge of the seal lip and the one end surface of the inner ring is larger than the diameter (D 9) of a groove bottom of the inner ring raceway. an outer ring provided with an outer ring raceway around an inner-circumferential surface thereof; an inner ring provided with an inner ring raceway around an outer-circumferential surface thereof, having one end surface that is a flat surface with which a positioning member for regulating the position in the axial direction of the inner ring comes in contact, and located on an inner-diameter side of the outer ring so as to be concentric with the outer ring; a plurality of rolling bodies located in an internal bearing space that is formed between the outer ring and the inner ring, and arranged between the inner ring raceway and the outer ring raceway so as to be able to roll freely; and a seal ring fastened to one end portion of the outer ring; characterized in that the one end surface of the inner ring is located at a position further recessed in the axial direction than one end surface of the outer ring, the seal ring has a circular ring shape and comprises: an elastic member made of an elastic material and having a seal lip provided with a tip-end edge that comes in sliding contact with the one end surface of the inner ring; and a circular ring-shaped metal core reinforcing the elastic member, the inner diameter of the metal core is larger than the outer diameter of the inner ring, and the inner ring raceway of the inner ring is composed of a deep-groove inner ring raceway, and the diameter (D 23) of the sliding contact portion between the tip-end edge of the seal lip and the one end surface of the inner ring is larger than the diameter (D 9) of a groove bottom of the inner ring raceway.