The present disclosure relates to a knee joint augment having an anatomical shape. More specifically, the present disclosure relates to a knee joint augment that is used for artificial joint replacement to replace lost bone, wherein the augment is used in artificial knee replacement surgery to be coupled to a knee implant. The augment includes a top surface configured to be brought into contact with a distal surface of a base plate that forms the body of a tibia element and a bottom surface configured to be brought into contact with a cut surface of a tibia. The bottom surface has an area smaller than that of the top surface, and has a tapered shape that narrows from the top to the bottom. An intermediate line at which one end surface cut to be perpendicular to the top surface and an outer surface meet each other has a shape that is outwardly convex to the outside of the augment with respect to a straight line connecting a top point where the intermediate line and the top surface meet and a bottom point where the intermediate line meets the bottom surface, whereby the intermediate line has a shape corresponding to the anatomical shape of a cut bone.