An artificial knee joint, which makes a drag (a contact stress) acting on a sliding surface upon bending small so as to evade an extraordinary abrasion and damage of a sliding surface of a tibia component and which prevents an bending angle from being decreased by preventing lifting of a femoral component in a rotational movement. The artificial knee joint comprises a femoral component to be secured to a distal portion of a femur and a tibia component to be secured to a proximal portion of a tibia, comprising an inner sliding surface and an outer sliding surface receiving a load of the femoral component at the tibia component.In the inner sliding surface, both of a front side and a rear side are formed in a sectional shape of circular arc in the front-to-back direction thereof, while in the outer sliding surface, a front side is formed in a sectional shape of a circular arc and a rear side is formed in a linear sectional shape in the front-to-back direction thereof.