A fixing mechanism for closed distal femur osteotomy according to an embodiment of the present invention is a fixing mechanism for distal femur osteotomy installed on a distal femur, which has been incised by closed distal femur osteotomy, the fixing mechanism comprising: a body portion, which is forced against the femur, and which has a plurality of coupling holes and long holes formed thereon; a head portion, which is connected to an end of the body portion, and which has a plurality of coupling holes formed thereon; screws inserted into the coupling holes; and sliding screws inserted into the long holes in adjusted coupling positions, wherein the head portion is formed to have a predetermined angle of inclination in the upward direction with regard to the lower surface of the head portion.