Serious failure on the slope of rock ground can be caused by a cyclic action of freezing and thawing in the cold regions. The frost susceptibilityand the effect of freezing and thawing on the rock material, however, have notbeen well investigated. In order to find out the freezing effect on the rock materials, mortar specimens are frozen as a pseudo-rock material under the constant rate of freezing by means of controlling the temperature of both endsof specimen. The freezing process is given one-dimensionally to the cylindrical samples in the laboratory to simulate the in-situ freezing phenomena in the natural ground. Formation of ice lens, frost heave and water intake during freezing process are observed on the mortar specimen under constant freezing rate, which probably causes cracks or large deformation in the real rock ground. The valuesof the velocity of elastic wave propagation are compared before and after freezing process to estimate the degree of weathering due to freezing and thawing.