Abstract: An artificial knee joint comprising a femoral component secured to the distal portion of a femur and a tibial component secured to the proximal portion of a tibia so that both the components are brought into sliding contact with each other via sliding surfaces, wherein the femoral component is provided on a rear central section of the sliding surface with a spherical or elliptical convex sliding surface and the tibial component is provided on the rear central section of the sliding surface with a spherical or elliptical concave sliding surface so that both the sliding surfaces are brought into sliding engagement when the artificial knee joint comprising the femoral and tibial components is bent deeply, whereby a person with this artificial knee joint can take a deep knee bending posture when sitting, which cannot be attained by conventional technology.