The evaluation of wave-induced seabed response has been recognised as a dominant factor in analyzing the seabed instability in the vicinity of a breakwater. Most previous investigations for wave-induced pore water pressure have been limited to two-dimensions, which are not able to simulate the phenomenon around the head of a breakwater. In this study, a three dimensional model for the wave-induced pore pressure around the head of a breakwater is established for both oscillatory and residual mechanisms. Numerical results conclude: (1) diffracted wave components significantly affect the distribution of pore water pressure and vertical effective normal stresses and liquefaction potential; (2) a liquefied hole occurs near the head of a breakwater; (3) incident wave angles do not only affect the pattern of liquefied regions, but also the maximum liquefaction depth; (4) the soil types significantly affect the distribution of soil response and liquefaction, and liquefaction only occurs in fine sand, not coarse sand.