Pneumatic tire

Pneumatic tire including a sipe formed in a tread block capable of minimizing slippage on a snowy or icy road while increasing rigidity of the tread block, thereby significantly improving braking and steering performances on wet and dry roads. The sipe comprises a first and a second sipe wall facing each other. The first sipe wall includes a plurality of upper protrusions extending from the surface of the tread block to a lower side thereof, a plurality of lower protrusions extending from the bottom of the sipe to an upper side thereof, and intermediate convex protrusions disposed between the upper and the lower protrusion in a radial direction of the tread block. The second sipe wall is formed with a phase difference of 1/2 of a pitch of the upper protrusion or the lower protrusion with respect to the first sipe wall so as to engage with the latter.