The present invention relates to a fixing tool for an open-wedge high tibial osteotomy, and the fixing tool for an open-wedge high tibial osteotomy, which is installed on a tibia cut open due to an open-wedge tibial osteotomy, includes: a fixing plate which includes a head portion that has a plurality of head nut holes, and an elongated plate that has an upper nut hole, a lower nut hole, and a long hole formed between the upper nut hole and the lower nut hole, and protrudes from one side of the head portion； screws which are coupled to the head nut holes, the upper nut hole, and the lower nut hole so as to fix the fixing plate to the tibia； and a support screw which is installed by being moved along the long hole formed to be spaced apart at a predetermined interval from the upper nut hole formed at a side adjacent to the head portion. Therefore, the fixing tool is closely fixed to a tibia, which has been cut open due to a procedure of a high tibial osteotomy, thereby enabling solid union of the tibia.
