This paper discusses about balancing control of unicycle robot.Unicycle robot consists of pitch which acts like inverted pendulum and roll which acts like reaction wheel pendulum.The robot which does not have actuator located in yaw axis is made to derive the simple dynamics.Lagrange equation is applied to deriving dynamic equations.Obtained dynamic equations are used to design the sliding mode control.State variables of the designed control are pitch angle and roll angle.Sliding mode control has chattering problem,which is eliminated by using the sigmoid function as switching function.Finally the control performance and eliminated chattering problem is verified by simulation. This paper discusses about balancing control of unicycle robot. Unicast robot consists of pitch which acts like inverted pendulum and roll which acts like reaction wheel pendulum. The robot which does not have actuator located in yaw axis is made to derive the simple dynamics. Lagrange equation is applied to deriving dynamic equations. Obtained dynamic equations are used to design the sliding mode control. State variables of the designed control are pitch angle and roll angle. Sliding mode control has chattering problem, which is eliminated by using the sigmoid function as switching function .Finally the control performance and eliminated chattering problem is verified by simulation.