The present invention relates to a fixing tool for an open-wedge high tibial osteotomy, and a fixing tool for an open-wedge high tibial osteotomy, which is installed on a tibia cut open due to a tibial osteotomy, includes: a fixing plate which includes a head portion that has a plurality of nut holes, and an elongated plate that has a plurality of nut holes and a long hole and is formed to protrude from one side of the head portion screws which are coupled to the nut holes and a block which is detachably installed in the long hole by using a fixing screw. 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.
