The invention belongs to the technical field of mechanical arms, discloses a mechanical arm and solves the problem of inconvenience in mounting and demounting of an existing mechanical arm. The mechanical arm comprises a base and an arm on the base and is characterized in that the base comprises a fixing seat and a mounting seat, and the mounting seat is in detachable connection with the fixing seat; the fixing seat comprises a horizontal top plate, a foundation and a first supporting plate, the foundation is positioned below the top plate, the first supporting plate is positioned between the top plate and the foundation, upper and lower ends of the first supporting plate are fixedly connected with the top plate and the foundation respectively, and the arm is arranged on the top plate; the mounting seat comprises a vertical first mounting plate and a second mounting plate, and the second mounting plate is vertically fixed to the first mounting plate and positioned between the first mounting plate and the first supporting plate. Since the detachable mounting seat is arranged on the fixing seat of the mechanical arm, mounting and demounting of the mounting seat have no influences on the fixing seat and the arm, and convenience in mounting and demounting of the base of the mechanical arm is achieved.