A robot 1 is equipped with a leg 2 including a knee joint 16 connecting a thigh link 32 and a crus link 34. The knee joint 16 is equipped with a connecting rod 44, one end of which is connected so as to be freely rotatable with respect to an axis 40 of the crus link 34 and the other end of which is connected so as to be freely rotatable to an axis 42 of the thigh link 32, and a distance varying mechanism 50 which changes the distance between an axis 60 of the crus link 34 and an axis 56 of the thigh link 32 by a driving force of an electric motor 40. When a bending angle of the knee joint 16 is 0 degree, a sum of the distance between the axis 40 and axis 42 and the distance between the axis 60 and the axis 56, is smaller than the distance between the axis 40 and the axis 56.