The effect of membrane thickness on the liquefaction resistance of sands was studied by means of the undrained and drained cyclic triaxial tests, the rebound tests, and the membrane strength and penetration tests. The latex membranes used are 0.18,0.25 and 0.60mm in thickness. It was found that : (1) the correction values of the membrane strength for the liquefaction resistance increased with increasing thickness of the membrane