The present invention provides a pneumatic radial tire for heavy load, having lug grooves in respective side regions of a tread surface, in which tire an amount of slip of the trailing edge of each of land portions defined by the lug grooves, with respect to a road surface, when the tire is rotated with load applied thereon is advantageously reduced without causing decrease in partial wear resistance of the land portions at a road contact surface thereof and generating cracks at the lug groove bottom. The pneumatic radial tire for heavy load, having a plurality of lug grooves 2 provided in respective side regions of a tread surface 1 to extend in the tread width direction, open at respective side edges of the tread surface 1, and define land portions 3 therebetween, is characterized in that: in a cross section of each lug groove 2 in the width direction thereof, only a groove wall 4 on the step-in side of each land portion 3 is bent at at least one bent point in the depth direction of the corresponding lug groove 2 such that a portion 4a 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.