Experiments on the liquefaction of the saturated sand contained a little clay, were carried out by the simple shear test, in order to clarify the effect of the cohesion and clay contents on liquefaction. As seen the record of the test (Fig. 2), sinusoidal shearing stress applied to a sample in the apparatus, utilizing two double action air cylinder. Soils used in the experiment are Shingu sand contained clay at the rate of about 5～15%.