A heavy duty radial tire including a tread portion which is provided with blocks having acute angled corners each defined between a pair of edge lines (3A and 3B) of the block, the acute angled corners being provided with a down slope which becomes steeper from the radially outside to the inside of the tire. Preferably, the size of the slope is 1 to 10 mm along the one edge line (3A), and 1 to 10 mm along the other edge line (3B), and 5 to 13 mm in the radial direction of the tire.