A crossed roller bearing comprising: an inner ring and an outer ring; a roller raceway that is formed between an inner ring-side V-groove formed in an inner-ring outer circumferential surface and an outer ring-side V-groove formed in an outer-ring inner circumferential surface; a plurality of rollers inserted into the roller raceway; a roller insertion groove formed in the inner ring for inserting the rollers into the roller raceway; and a plug for sealing the roller insertion groove, wherein the inner ring-side V-groove has: a pair of inclined raceway surfaces (35, 36) along which the rollers roll; a concave surface formed between the inclined raceway surfaces (35, 36) so as to not contact with the rollers; and a minimum outer diameter section of the inner ring, the minimum outer diameter section being located within the concave surface, wherein the roller insertion groove has: an end face-side groove opening that exposes to one of ring-shaped end faces of the inner ring; and an outer circumferential surface-side groove opening that continues to the end face-side groove opening and exposes to the inner ring-side V-groove in the inner-ring outer circumferential surface, wherein the outer circumferential surface-side groove opening is defined by a circumferential direction opening edge extending in a circumferential direction along the inner ring-side V-groove and a pair of side opening edges (62b, 62c) extending from both ends of the circumferential direction opening edge to the ring-shaped end faces, and the circumferential direction opening edge of the roller insertion groove is formed at a position deviated from the minimum diameter section of the concave surface, wherein the circumferential direction opening edge of the roller insertion groove is formed at an opposite position to the ring-shaped end face relative to the minimum outer diameter section characterized in that where a distance from the ring-shaped end face to the minimum outer diameter section is D38, a width of the curved surface is W37 and a groove depth of the roller insertion groove which is a distance from the ring-shaped end face to the circumferential direction opening edge is D6, D 38 < D 6 < D 38 + W 37 / 2 is satisfied. an inner ring and an outer ring; a roller raceway that is formed between an inner ring-side V-groove formed in an inner-ring outer circumferential surface and an outer ring-side V-groove formed in an outer-ring inner circumferential surface; a plurality of rollers inserted into the roller raceway; a roller insertion groove formed in the inner ring for inserting the rollers into the roller raceway; and a plug for sealing the roller insertion groove, wherein the inner ring-side V-groove has: a pair of inclined raceway surfaces (35, 36) along which the rollers roll; a concave surface formed between the inclined raceway surfaces (35, 36) so as to not contact with the rollers; and a minimum outer diameter section of the inner ring, the minimum outer diameter section being located within the concave surface, a pair of inclined raceway surfaces (35, 36) along which the rollers roll; a concave surface formed between the inclined raceway surfaces (35, 36) so as to not contact with the rollers; and a minimum outer diameter section of the inner ring, the minimum outer diameter section being located within the concave surface, wherein the roller insertion groove has: an end face-side groove opening that exposes to one of ring-shaped end faces of the inner ring; and an outer circumferential surface-side groove opening that continues to the end face-side groove opening and exposes to the inner ring-side V-groove in the inner-ring outer circumferential surface, an end face-side groove opening that exposes to one of ring-shaped end faces of the inner ring; and an outer circumferential surface-side groove opening that continues to the end face-side groove opening and exposes to the inner ring-side V-groove in the inner-ring outer circumferential surface, wherein the outer circumferential surface-side groove opening is defined by a circumferential direction opening edge extending in a circumferential direction along the inner ring-side V-groove and a pair of side opening edges (62b, 62c) extending from both ends of the circumferential direction opening edge to the ring-shaped end faces, and the circumferential direction opening edge of the roller insertion groove is formed at a position deviated from the minimum diameter section of the concave surface, wherein the circumferential direction opening edge of the roller insertion groove is formed at an opposite position to the ring-shaped end face relative to the minimum outer diameter section characterized in that where a distance from the ring-shaped end face to the minimum outer diameter section is D38, a width of the curved surface is W37 and a groove depth of the roller insertion groove which is a distance from the ring-shaped end face to the circumferential direction opening edge is D6, D 38 < D 6 < D 38 + W 37 / 2 is satisfied.