A roller bearing comprising: an outer ring having an outer ring raceway surface on an inner peripheral surface; an inner ring having an inner ring raceway surface on an outer peripheral surface; a plurality of rolling elements rotatably arranged between the outer ring raceway surface and the inner ring raceway surface; and a seal member that is fixed to a seal attachment groove formed in an axially end portion of the outer ring by a snap ring and seals an axially end portion of a bearing internal space between the outer ring and the inner ring, wherein an outer diameter of the seal member is larger than an outer diameter of the snap ring in the seal attachment groove, wherein a radially outer end portion of the seal member is sandwiched between an inner peripheral surface of the seal attachment groove and an outer peripheral surface of the snap ring, wherein the seal attachment groove includes a groove bottom surface with which an outer peripheral surface of the seal member is in contact, and a groove inner side surface that is provided on an axially inner side of the groove bottom surface and with which an axially inner side surface of the seal member is in contact, characterized in that the seal attachment groove includes a tapered surface that is provided on an axially outer side of the groove bottom surface, that connects the groove bottom surface and an inner peripheral surface of the outer ring, and with which the snap ring is in contact, and a step portion provided at a boundary portion between the groove bottom surface and the groove inner side surface. an outer ring having an outer ring raceway surface on an inner peripheral surface; an inner ring having an inner ring raceway surface on an outer peripheral surface; a plurality of rolling elements rotatably arranged between the outer ring raceway surface and the inner ring raceway surface; and a seal member that is fixed to a seal attachment groove formed in an axially end portion of the outer ring by a snap ring and seals an axially end portion of a bearing internal space between the outer ring and the inner ring, wherein an outer diameter of the seal member is larger than an outer diameter of the snap ring in the seal attachment groove, wherein a radially outer end portion of the seal member is sandwiched between an inner peripheral surface of the seal attachment groove and an outer peripheral surface of the snap ring, wherein the seal attachment groove includes a groove bottom surface with which an outer peripheral surface of the seal member is in contact, and a groove inner side surface that is provided on an axially inner side of the groove bottom surface and with which an axially inner side surface of the seal member is in contact, a groove bottom surface with which an outer peripheral surface of the seal member is in contact, and a groove inner side surface that is provided on an axially inner side of the groove bottom surface and with which an axially inner side surface of the seal member is in contact, characterized in that the seal attachment groove includes a tapered surface that is provided on an axially outer side of the groove bottom surface, that connects the groove bottom surface and an inner peripheral surface of the outer ring, and with which the snap ring is in contact, and a step portion provided at a boundary portion between the groove bottom surface and the groove inner side surface. a tapered surface that is provided on an axially outer side of the groove bottom surface, that connects the groove bottom surface and an inner peripheral surface of the outer ring, and with which the snap ring is in contact, and a step portion provided at a boundary portion between the groove bottom surface and the groove inner side surface.