We investigated the ferroelectric characteristics of an epitaxial perovskite ZnSnO(3) thin film on a (111) SrRuO(3)/(111) SrTiO(3) substrate fabricated by pulsed laser deposition. We confirmed that the ZnSnO(3) thin film was epitaxially grown on the substrate, forming large terraces on the surface of the ZnSnO(3) thin film. The ZnSnO(3) thin film exhibited a high ferroelectric polarization of approximately 47 microC/cm(2), which was further supported by first-principles calculations.