This study deals with derivation of equivalent horizontal stiffness and seismic analysis of Heunginjimun based on ambient vibration test, which give its natural frequencies, modes and damping ratios. Natural frequencies are identified as invariant values. Lowest two lateral modes in weak axis shows that columns under acceleration sensing moves in parallel with same phase. They mean that Heunginjimun behaves linearly and not individually under ambient vibration. Beam-column joints are much weak compared to individual column stiffness. All these founding allows Heunginjimun to be modelled as dynamic rigid body with two stories having vertical compressive forces, which are estimated by self loads. Rigid body model with two degrees of freedom is suggested and characteristic equation is derived. Lateral stiffnesses of the model are found from the equation with identified natural frequencies. These identified data make possible to perform equivalent static and dynamic seismic analyses by Korean Building Code and Commentary-2009. Story drifts of the model are obtained by two analyses showing that the second story drift exceeds the allowable drift.