In this paper, unsteady forces of wet-steam flows through real steam turbine low pressure final three stages developed by Mitsubishi Heavy Industry are numerically investigated. Compressible Nervier-Stokes equations coupled with nonequilibrium condensation models are simultaneously solved. The SST-model is also employed for evaluating the eddy-viscosity. Time-dependent pressure distributions on three-stage stator-rotor blade surfaces at constant spans are plotted to show the magnitude and the variation of unsteady forces locally. And then, the flow mechanism, how such unsteady forces are generated from the wet-steam flow through the multi-stage blade rows, is predicted.