A numerical method for analysis of three-dimensional stress waves in an elastic/viscoplastic thick plate is presented, when an oblique impact is applied to the surface of the thick plate at various impact angles. For the numerical analysis, the finite difference method based on integration along bicharacteristics is employed. By obtaining the numerical results for various cases of loading conditions, the effect of the impact angle on impact fracture is examined. It is also demonstrated that dynamic behavior of the plate due to oblique impact can be examined in detail by this method.