Lateral movement of a strip in the hot rolling process is an important unsolved technical problem. It results in reduced productivity and, in the extreme case, in strip tearing during tailing out at the finishing mill. Lateral movement of a strip is caused by various asymmetric factors such as mechanical asymmetry of the mill, and different temperatures along the strip width direction. This study aims to understand the influences of these various factors on lateral movement, and to develop a controller that is useful for reducing lateral movement. Mathematical models which consider initial off-center value, leveling error of the mill, and strip tension for lateral movement of the strip are proposed. A Proportional-Integral- Derivative(PID) based sliding mode controller using an observer is also proposed to prevent lateral movement of strips. In addition, a control algorithm is designed to solve the chattering problem of a sliding mode control. The effectiveness of the proposed method is evaluated by numerical simulation of hot rolling by a pinch roll.