Pneumatic tire for running on rough terrain

A pneumatic tire for rough terrain comprises a tread portion with a tread pattern provided with a block having a height of from 10 to 19 mm, the block comprising a top face and a sidewall face extending radially inwardly from a peripheral edge of the top face, the top face being a polygonal shape with a plurality of sides equal to or more than four, the sidewall face comprising a plurality of slant surfaces extending radially inwardly away from the sides, respectively, wherein each slant surface comprises a radially outer portion and a radially inner portion, the radially outer portion has a flat plane, the radially inner portion comprises a first plane and a second plane laterally adjacent to said first plane, and the first plane and second plane cross each other so that said radially inner portion dents inwardly of the block.