The free surface shock wave (FSSW) generated by a wedge model is numerically studied. The numerical simulations performed by the finite difference method employing density function method show the systematic variation of the shock phenomenon due to the Froude number based on the draft as obtained by experiments. The typical nonlinear phenomena like wave breaking and abrupt changes of velocity vectors are successfully captured and the details of wave breaking induced by the FSSW are clarified. Wave breaking occurs to weaken the nonlinearity and shear vortex and longitudinal vortex are generated from the overturning point on the free surface. After the wave breaking a steep wave is reproduced due to the nonlinearity. This seems to be periodically repeated.