In this paper, the robust controller design problem for active vibration control of seismic-excited building structures by means of pole placement method is studied. In particular, the building structures are assumed to have parameter uncertainties, and the design of controller will assure the pole locations of the closed-loop system are inside an indicated subregion on the left-hand side of complex plane in spite of the parameter uncertainties. For the building models, the parameter uncertainties dealt with belong to the polytope type uncertainties and are assumed to be the variations of the structural masses, stiffnesses, and damping coefficients. The quadratic stability test using the fixed quadratic Lyapunov function is studied and the sufficient conditions for the existence of a robust stabilising state feedback controller are presented as linear matrix inequalities (LMIs). The performance of the presented approach is demonstrated by numerical simulations on the vibration control of building structure subject to seismic excitation. It is confirmed that the designed controller can effectively attenuate the structural vibration when the parameter uncertainties exist.