Two wheel mobile manipulator has the potential to become multi-skilled robot in the field of robotics engineering and it is already implemented by using inverted pendulum control. Centre of gravity position is controlled to achieve the balancing of robot. Due to the unbalanced nature and the nonholonomic property of the two-wheel mobile manipulator, balancing is challenging task. On the other hand sliding mode control is a good candidate to address the nonlinear/under actuated system. This paper presents the control methods for balancing of two-wheel mobile manipulator. This paper proposes a novel second order sliding mode controller using twisting algorithm, disturbance observer and dynamics of double inverted pendulum. Dynamics of double inverted pendulum is used to design the control equation of sliding mode controller. Twisting algorithm is used to design the control input. Disturbance observer is compensated model uncertainties and external disturbances. Posture of two wheel mobile manipulator can successfully stabilized by this novel controller.