The scouring around the coastal structure is one of the important problems for the design and construction of the strcuture.
　But it remains unclear and so, the field engineers depend on their experience to protect the structure against the damage by scouring.
　Then, authors have taken up an extensive study on scouring containning field observations and model experiments.
　At the first step, the scouring at the foot of vertical wall was tested in the wave channel with waves of 8.7, 26.0 and 42.0 cm in height and 1.3, 3.0 and 5.1 sec in period.
　A vertical wall was installed at various points of the equilibrium profile for each waves.
　The results are summarized as follows;
　1) The phenomena of scouring are classified into 4 groups from the viewpoint of the time change of scouring depth.
　2) The change of return flow along the bottom and the occurence of reflected waves dur to the wall play important roles in the phenomena of scouring at the foot of wall.
　3) The maximum scouring appears when the wall is installed near the plunging point of breaking waves.
　4) The distribution of scouring depth along the beach profile is of V shape for the normal beach and of W shape for the storm beach.