Silica-supported silver exhibited high catalytic activity in the dehydration of glycerol: glycerol was dehydrated into hydroxyacetone with the selectivity higher than 86% at 91% conversion over Ag/SiO2 in H-2 flow at 240 degrees C. Silver metal provides an active site and showed stable catalytic activity for the glycerol dehydration in H-2 atmosphere, while the dehydration activity decreased in N-2 atmosphere. The hydrogenation of hydroxyacetone into 1,2-propanediol and the decomposition to ethylene glycol did not proceed over silver.