PURPOSE: To improve driving performance on the uneven ground by providing sub-grooves shallower than main grooves and shifting the mutual position of a pair of block pieces.

CONSTITUTION: The tread pattern on a tire 1 is formed by main grooves 2 and block group A1, A2,.... Sub-grooves 3 shallower than the main grooves 2 is arranged from the one side surface of the block to the other side surface of the opposite side on the surface of at least one block among the block group A1, A2,.... The first block A1 having the structure of which length is sectional direction is longer than the length in circumferential direction is arranged on the central part CL via the main grooves. A pair of block pieces divided by the sub- grooves are shifted each other. The first block A1 having the structure of which length in the sectional direction is longer than the length is circumferential direction is arranged on the central part CL via the main grooves 2. The second block A2, the third block A3 having the structure of which length in circumferential direction is longer than the length in sectional direction, the forth block A4, the fifth block A5 having the structure of which length in sectional direction is longer than the length in circumferential direction are arranged from the central part to the shoulder part via the main grooves 2.