Artificial reef has been used as a measure to reduce wave energy off to the beach. However, reef body erosion due to return flow on the gap between artificial reefs has been reported. Moreover, most of past studies dealt with sandy beach and permeability of sea bed has not been investigated in depth. Hence, this study aims to investigate characteristics of flow field around artificial reef considering the permeability of sea bed through 2D and 3D numerical simulations. As a result, the permeability affects a return flow, which leads to change in water velocity field. Results of 3D simulation show that the flow field formed around an artificial reef can explain sediment transport around it.