A bone plate comprising: a strip-shaped body portion to be fixed to a portion of the lateral surface of a tibia (X) below an osteotomy surface formed in the lateral surface of the tibia (X), the body portion being configured to extend along a longitudinal direction of the tibia (X); a wide portion wider than the body portion and to be fixed along an outer peripheral surface of the head of the tibia (X) at a higher position than the osteotomy surface; a connecting portion that connects the body portion and the wide portion ; and a plurality of screw holes arrayed in the wide portion , the body portion , and the connecting portion with spaces between one another and penetrate therethrough in a plate thickness direction, wherein an inner surface of the bone plate that extends from the wide portion to the connecting portion and that faces, in use, the tibia (X) is continuously curved so as to be twisted about an axis along the longitudinal direction, the wide portion is offset in an outward plate thickness direction with respect to the body portion , and when the bone plate is attached to the tibia (X), a curvature of a side surface of the connecting portion that follows the posterior surface of the tibia (X) is larger than a curvature of a side surface of the connecting portion that follows the anterior surface of the tibia (X), characterized in that a twist angle of the bone plate is set to 13 ± 5°, and a radius of curvature of the connecting portion on a side that follows a posterior surface of the tibia (X) is set to 12.5 ± 7.5 mm, and the radius of curvature of the connecting portion on the side that follows the anterior surface of the tibia (X) is set to 90 ± 30 mm. a strip-shaped body portion to be fixed to a portion of the lateral surface of a tibia (X) below an osteotomy surface formed in the lateral surface of the tibia (X), the body portion being configured to extend along a longitudinal direction of the tibia (X); a wide portion wider than the body portion and to be fixed along an outer peripheral surface of the head of the tibia (X) at a higher position than the osteotomy surface; a connecting portion that connects the body portion and the wide portion ; and a plurality of screw holes arrayed in the wide portion , the body portion , and the connecting portion with spaces between one another and penetrate therethrough in a plate thickness direction, wherein an inner surface of the bone plate that extends from the wide portion to the connecting portion and that faces, in use, the tibia (X) is continuously curved so as to be twisted about an axis along the longitudinal direction, the wide portion is offset in an outward plate thickness direction with respect to the body portion , and when the bone plate is attached to the tibia (X), a curvature of a side surface of the connecting portion that follows the posterior surface of the tibia (X) is larger than a curvature of a side surface of the connecting portion that follows the anterior surface of the tibia (X), characterized in that a twist angle of the bone plate is set to 13 ± 5°, and a radius of curvature of the connecting portion on a side that follows a posterior surface of the tibia (X) is set to 12.5 ± 7.5 mm, and the radius of curvature of the connecting portion on the side that follows the anterior surface of the tibia (X) is set to 90 ± 30 mm. <EOS>