A pneumatic tire having enhanced on-ice braking performance achieved by further increasing the amount of water that can be sucked up into sipes. In the pneumatic tire, blocks (26) partitioned by circumferential grooves and lateral grooves are formed in the tread. A sipe (28) is formed in a block (26), and a fine structure (32) having a height in the range of from 1/50 of the sipe width t to less than 1/10 of the sipe width t is formed on a sipe wall surface. This reduces fluid friction coefficient of water relative to the sipe wall surface to a lower level than conventional products. As a result, when water staying on ice comes into contact with the sipe wall surface, the water is more easily sucked up into the sipe. The construction increases the amount of water that can be sucked up into the sipe (28) or the removal amount of water that stays on ice etc., and this enhances braking performance (friction characteristics) on ice.