The real sea waves are quite random in height, period and propapgation direction. Therefore, they are called directional random waves or short crested waves.
　It is of great importance to reproduce directional random waves in a laboratory basin for hydraulic model tests. The Port and Harbour Research Institute has built a serpent-type wave generator in order to generate directional random waves similar to real sea waves. It has been installed in the experimental basin of 36m wide and 24m long and composed of 35 piston-type wave-makers. Each wave maker has a wave paddle of 80cm wide and 140cm high. The present report discribes the experimental characteristics of uni and multi-directional random waves generated by the serpent-type wave generator.
　The following conclusions have been drawn from the result of spectral analysis.
1) The wave energy of the oblique uni-directional random waves shows the directional distribution wider than that of the uni-directional random waves with the oblique angle of 0°.
2) The value of Smax which indicates the angular spreading parameter becomes smaller than the target one for the case of large value of Smax, while it becomes larger than the target one for the case of small value of Smax because of the finite total width of the wave paddles.