Machinery and robot arm

The invention discloses a mechanical arm which comprises two arm members and a rod piece. The two arm members are connected in a rotating mode, the two ends of the rod piece are movably connected with the two arm members respectively and move in the axial directions of the two arm members respectively so as to drive the mechanical arm to be folded and unfolded. According to the mechanical arm, a labor-saving lever is formed by driving the two ends of the rod piece to move in the axial directions of the arm members respectively, and the two arm members are driven to rotate relatively to be folded and unfolded. Thus, a driving motor of small power can be adopted. Moreover, the driving motor is not limited to be arranged in the rotating connection position of the two arm members, so that the rotating connection position of the two arm members is allowed to be of other space design, and the degree of design freedom is increased. The invention further discloses a robot comprising the mechanical arms.