A sealing device (20, 21, 50, 60) used in a rolling bearing comprising an inner member (4, 78) and an outer member that rotate relative to each other, the inner member (4, 78) comprising a cylindrical part and a flange (4B, 78B) expanding radially outward from the cylindrical part, the cylindrical part and the flange (4B, 78B) of the inner member (4, 78) comprising machining marks in a shape of spiral grooves, the sealing device (20, 21, 50, 60) located between the inner member (4, 78) and the outer member of a rolling bearing for sealing a gap between the inner member (4, 78) and the outer member, the sealing device (20, 21, 50, 60) comprising: a mounted part (38, 56B, 61, 71) that is to be mounted on the outer member of the rolling bearing; an inner annular part (24B, 54C, 64B) extending radially inward from the mounted part (38, 56B, 61, 71); a grease lip formed of an elastic material extending from the inner annular part (24B, 54C, 64B) toward the cylindrical part of the inner member (4, 78) of the rolling bearing, the grease lip being in slidable contact with the cylindrical part of the inner member (4, 78) of the rolling bearing; a side lip formed of an elastic material extending from the inner annular part (24B, 54C, 64B) toward the flange (4B, 78B) of the inner member (4, 78) of the rolling bearing, the side lip being in slidable contact with the flange (4B, 78B) of the inner member (4, 78) of the rolling bearing and being in contact with the machining marks on the flange (4B, 78B), so that the machining marks on the flange (4B, 78B) serves as a feed screw for the side lip; and a thin plate-like intermediate lip formed of an elastic material extending from the inner annular part (24B, 54C, 64B) toward the inner member (4, 78) of the rolling bearing, the intermediate lip being arranged intermediate between the grease lip and the side lip, the intermediate lip being in slidable contact with the inner member (4, 78) of the rolling bearing, characterized in that the grease lip is in contact with the machining marks on the cylindrical part, so that the machining marks on the cylindrical part serves as a feed screw for the grease lip, the intermediate lip is disposed radial inside of the side lip and overlapping with the side lip, and is in contact with the machining marks on the inner member (4, 78), so that the machining marks on the inner member (4, 78) serves as a feed screw for the intermediate lip, and a contact width of the side lip to the flange (4B, 78B) is less than 0.041 mm in a case in which the sealing device (20, 21, 50, 60) is mounted on the rolling bearing, the contact width being defined as a contact length between a surface of the side lip and the flange (4B, 78B) in radial directions of the sealing device (20, 21, 50, 60). a mounted part (38, 56B, 61, 71) that is to be mounted on the outer member of the rolling bearing; an inner annular part (24B, 54C, 64B) extending radially inward from the mounted part (38, 56B, 61, 71); a grease lip formed of an elastic material extending from the inner annular part (24B, 54C, 64B) toward the cylindrical part of the inner member (4, 78) of the rolling bearing, the grease lip being in slidable contact with the cylindrical part of the inner member (4, 78) of the rolling bearing; a side lip formed of an elastic material extending from the inner annular part (24B, 54C, 64B) toward the flange (4B, 78B) of the inner member (4, 78) of the rolling bearing, the side lip being in slidable contact with the flange (4B, 78B) of the inner member (4, 78) of the rolling bearing and being in contact with the machining marks on the flange (4B, 78B), so that the machining marks on the flange (4B, 78B) serves as a feed screw for the side lip; and a thin plate-like intermediate lip formed of an elastic material extending from the inner annular part (24B, 54C, 64B) toward the inner member (4, 78) of the rolling bearing, the intermediate lip being arranged intermediate between the grease lip and the side lip, the intermediate lip being in slidable contact with the inner member (4, 78) of the rolling bearing, characterized in that the grease lip is in contact with the machining marks on the cylindrical part, so that the machining marks on the cylindrical part serves as a feed screw for the grease lip, the intermediate lip is disposed radial inside of the side lip and overlapping with the side lip, and is in contact with the machining marks on the inner member (4, 78), so that the machining marks on the inner member (4, 78) serves as a feed screw for the intermediate lip, and a contact width of the side lip to the flange (4B, 78B) is less than 0.041 mm in a case in which the sealing device (20, 21, 50, 60) is mounted on the rolling bearing, the contact width being defined as a contact length between a surface of the side lip and the flange (4B, 78B) in radial directions of the sealing device (20, 21, 50, 60).