Water impact of a wedge is a very primitive but an essential phenomenon to wave impact loads on ships in waves. Investigations have been carried out extensively on water impact loads on ships and so many features are known today on water impact on wedges and ships. But, a few aspect is lack in them. It is a scaling law of water impact pressure. In reality, Froude scaling law is applied to utilize the model test results for full scale ships, implicitly or explicitly. On the other hand, many test results put a question to the appropriateness of Froude scaling law for the water impact pressure. Response of a panel to the water impact pressure is another problem. Some papers and reports proposed methods to estimate the impact pressure on full-scale ships and to calculate the response of structures to the impact pressure, in which impact pressure is applied to the structure as a stationary uniform impact load. But, actual impact pressure on a wedge moves on the surface of the wedge at very high velocity. The response of the structure to the different two types of loads must be different. In this context, Water impact test of a wedge was carried out to study the scaling law of water impact pressure and to study the response of a panel to the water impact pressure. The test result showed that non-dimensional peak pressure is affected by the distance between the pressure gage and the keel of the wedge. The farther and farther the distance is, the larger and larger the peak value is. But, there seems to be an upper bound to them, which is almost equal to Wagner's theoretical impact pressure for the wedge. This implies that the water impact pressure for a wedge might obey Wagner's theory, but a pressure gage might modify it. A simulation of a pressure gage by finite element analysis with Wagner's theoretical impact pressure indicates that the impact pressure is modified by the pressure gage to be an analogous one to the test results. The result of this analysis explains well the tendency of the test results. The effect of a pressure gage on the peak pressure depends on the ratio of the diameter of the pressure gage to the distance between the pressure gage and the keel of the wedge. A finite element analysis of the panel with Wagner's theoretical impact pressure as external loads, gave results which showed very good agreements with the test results. Furthermore, the analysis indicated that the response of the panel to the moving impact pressure, as is the actual one, is about one half or one-third of that to the stationary uniform impact pressure.