A depolarization phenomenon at 34.5 GHz due to wet snow was observed in a horizantal terrestrial path of 1.3 km. Data during snowfall show fairly large degradations of XPD in comparison with data during rain and theoretical values based upon the model of deformed raindrop, under the condition of the same copolar attenuation. Much larger deformation of snowflake than that of raindrop must be assumed to explain such inclination by the model of depolarization due to an oblate spheroidal snowflake. Effective differential propagation constants of snow, which are derived from measurements of XPD and phase difference between cross- and co-polar components, show that depolarization due to wet snow at 34.5 GHz comes from not only differential phase shift but also differential attenuation. A certain kind of anomalous depolarization on Earth-space paths may be explained by the model of depolarization due to wet snow.