Natural hazards like landslides, tsunami, earthquake, cyclone and volcanic eruption are most rigorous natural hazards in the environment that causes damage to structures. These natural calamities produce a potent remembrance because of heavy damage to the environment. Accordingly, a structural engineer faces a challenge of designing the structure which can tolerate the natural forces and protect all the structural member and dwellers, to all environmental forces like wind load, earthquakes, cyclones and tsunamis. In recent years, all the structures are designed with the earthquake protective system like passive protective system, active protective system and semi-active protective system for structural control. The semi-active protective system is preferred over others since it adopts the advantage of two systems as consistency of passive protective system and flexibility of active protective system. In this work, magnetorheological damper is chosen to regulate the vibration of a three-story benchmark structure. The damper is placed in between the ground and the first floor to produce required force by the structure which is excited for Kobe earthquake. This paper has considered the earthquake as uncertainty. Therefore, a robust controller is preferred because it produces the required controlled voltage to suppress the structural vibration even in the presence of the uncertainty. These controller parameters are tuned by ultimate gain method in MATLAB and Simulink. Current driver is used to convert the controlled voltage to controlled current and is applied to magnetorheological damper. This produces the controlled force which further is applied to the benchmark structure which is considered. Results obtained by robust controller and classical Proportional Integral Derivative (PID) controller are compared, and superiority of robust controller is presented.