A pneumatic radial tire for heavy load, having a plurality of lug grooves (2,12) provided in respective side regions of a tread surface (1, 11) to extend in the tread width direction, open at respective side edges of the tread surface (1, 11), and define land portions therebetween, characterized in that: in a cross section of each lug groove (2,12) in the width direction thereof, only a groove wall on the step-in side of each land portion is bent at at least one bent point (f) in the depth direction of the corresponding lug groove (2,12) such that a portion of the groove wall, located on the inner side in the radial direction than the bent point (f), is tilted in a direction that narrows a groove width, wherein: the bent point is positioned within the range of 30-70% of a groove depth of the lug groove (2,12) measured from a surface of the land portion; a portion located on the outer side in the radial direction than the bent point is tilted at an angle "a" with respect to a line normal to the surface of the land portion, which angle "a" falls in the range of 0-20°; a portion located on the inner side in the radial direction than the bent point is tilted at an angle "c" with respect to an imaginary line extended from the radially-outer-side portion, which angle "c" falls in a range of 5-15°; and a groove wall of the kick-out side of each land portion is tilted such that an angle "b" formed by the groove wall with respect to a line normal to the surface of the land portion satisfies a relationship of a-5° ≤ b ≤ a+5° and b ≥ 0°. in a cross section of each lug groove (2,12) in the width direction thereof, only a groove wall on the step-in side of each land portion is bent at at least one bent point (f) in the depth direction of the corresponding lug groove (2,12) such that a portion of the groove wall, located on the inner side in the radial direction than the bent point (f), is tilted in a direction that narrows a groove width, wherein: the bent point is positioned within the range of 30-70% of a groove depth of the lug groove (2,12) measured from a surface of the land portion; a portion located on the outer side in the radial direction than the bent point is tilted at an angle "a" with respect to a line normal to the surface of the land portion, which angle "a" falls in the range of 0-20°; a portion located on the inner side in the radial direction than the bent point is tilted at an angle "c" with respect to an imaginary line extended from the radially-outer-side portion, which angle "c" falls in a range of 5-15°; and a groove wall of the kick-out side of each land portion is tilted such that an angle "b" formed by the groove wall with respect to a line normal to the surface of the land portion satisfies a relationship of a-5° ≤ b ≤ a+5° and b ≥ 0°. the bent point is positioned within the range of 30-70% of a groove depth of the lug groove (2,12) measured from a surface of the land portion; a portion located on the outer side in the radial direction than the bent point is tilted at an angle "a" with respect to a line normal to the surface of the land portion, which angle "a" falls in the range of 0-20°; a portion located on the inner side in the radial direction than the bent point is tilted at an angle "c" with respect to an imaginary line extended from the radially-outer-side portion, which angle "c" falls in a range of 5-15°; and a groove wall of the kick-out side of each land portion is tilted such that an angle "b" formed by the groove wall with respect to a line normal to the surface of the land portion satisfies a relationship of a-5° ≤ b ≤ a+5° and b ≥ 0°.