This paper shows the detail of posture control of the Personal Mobility Robot (PMR). PMR is a two-leg-wheeled inverted pendulum type robot which supports daily personal mobility even in the limited indoor area. This mechanism minimizes the footprint occupied by PMR. To realize stability and controllability of inverted pendulum mobility, the three dimensional physical model based Linear-Quadratic Regulator (LQR) is applied. Then appropriate swing arm angles to maintain horizontal posture of roll posture are inputted to the LQR controller as a reference. Real world experiments have been carried out on trapezoidal obstacles. This demonstrates the stability of inverted pendulum control and roll posture control.