A heavy load pneumatic radial tire comprising: a tread comprising blocks (100, 200A) that contact a road surface, the blocks (100, 200A) being arranged in block rows extending in the tire circumferential direction, each block row comprising a plurality of blocks (100, 200A) arranged along the tire circumferential direction, each of the blocks of a first block row out of the block rows being defined by circumferential direction grooves extending in the tire circumferential direction and width direction grooves extending in the tire width direction, and each of the blocks of a second block row out of the block rows being formed at the outer sides in the tire width direction of the blocks of the first block row, respectively, and being defined by a circumferential direction groove extending in the tire circumferential direction and width direction grooves extending in the tire width direction; and a crossing belt layer arranged at an inner side in a tire radial direction with respect to the blocks (100, 200A), wherein: a sipe (110, 210A) extended in a tire width direction is formed in each block (100, 200A) to define smaller blocks; an inclined portion (120, 220) is formed in each block (100, 200A) on an end portion at a kick-out side of a smaller block defined by the sipe (110, 210A) at the transition between the radial end of the sipe (110, 210A) and the ground contact surface of the smaller block; the inclined portion (120, 220) is formed by chamfering the end portion at the kick-out side so as to be inclined inward from an outer side in the tire radial direction to an inner side in the tire radial direction; the inclined portion (120, 220) is formed in a region where the crossing belt layer is formed, in the tire width direction; and the inclined portion of the blocks of the second block row becomes narrower toward the outer side in the tire width direction and disappears at the belt end (Be) of the crossing belt layer. a tread comprising blocks (100, 200A) that contact a road surface, the blocks (100, 200A) being arranged in block rows extending in the tire circumferential direction, each block row comprising a plurality of blocks (100, 200A) arranged along the tire circumferential direction, each of the blocks of a first block row out of the block rows being defined by circumferential direction grooves extending in the tire circumferential direction and width direction grooves extending in the tire width direction, and each of the blocks of a second block row out of the block rows being formed at the outer sides in the tire width direction of the blocks of the first block row, respectively, and being defined by a circumferential direction groove extending in the tire circumferential direction and width direction grooves extending in the tire width direction; and a crossing belt layer arranged at an inner side in a tire radial direction with respect to the blocks (100, 200A), wherein: a sipe (110, 210A) extended in a tire width direction is formed in each block (100, 200A) to define smaller blocks; an inclined portion (120, 220) is formed in each block (100, 200A) on an end portion at a kick-out side of a smaller block defined by the sipe (110, 210A) at the transition between the radial end of the sipe (110, 210A) and the ground contact surface of the smaller block; the inclined portion (120, 220) is formed by chamfering the end portion at the kick-out side so as to be inclined inward from an outer side in the tire radial direction to an inner side in the tire radial direction; the inclined portion (120, 220) is formed in a region where the crossing belt layer is formed, in the tire width direction; and the inclined portion of the blocks of the second block row becomes narrower toward the outer side in the tire width direction and disappears at the belt end (Be) of the crossing belt layer. a sipe (110, 210A) extended in a tire width direction is formed in each block (100, 200A) to define smaller blocks; an inclined portion (120, 220) is formed in each block (100, 200A) on an end portion at a kick-out side of a smaller block defined by the sipe (110, 210A) at the transition between the radial end of the sipe (110, 210A) and the ground contact surface of the smaller block; the inclined portion (120, 220) is formed by chamfering the end portion at the kick-out side so as to be inclined inward from an outer side in the tire radial direction to an inner side in the tire radial direction; the inclined portion (120, 220) is formed in a region where the crossing belt layer is formed, in the tire width direction; and the inclined portion of the blocks of the second block row becomes narrower toward the outer side in the tire width direction and disappears at the belt end (Be) of the crossing belt layer.