We present an inference method for Green's functions for multistory torsionally coupled shear buildings, and demonstrate that it is a practical tool by an application to an existing building. We first show that horizontal vibrations of an individual floor are specified as a three-input-three-output linear system, introducing Green's functions in it. Then, we develop the inference method for discrete Green's functions by the Wiener filter. Applying the inference method to an 8-story torsionally coupled shear building, we obtain reliable Green's functions, correcting waveform deformation of Green's functions associated with the torsion. We also show that the effect of wind on Green's functions is negligibly small.