To prevent generation of soil congestion between lugs and to prevent damage of a plowed field by tilting the front end part of the lug at an angle within a specific range to the tire axis direction.

An inclination angle of a front end part 5 in a lug 4 to the tire axis direction is set to be a range from 10° to 45°. More desirably, the inclination angle ranges from 15° to 30°. When a wall face 6 in the lug front end part 5 is tilted at 30° or more to the tire diameter, soil can be excellently trodden down and damage of a plowed field can be prevented, however, a space between the lugs 4 in the vicinity of an equator is extremely narrowed contrarily and soil draining ability is lowered. However, when the inclination angle of the front end part 5 in the lug 4 to the tire axis direction is set to be a range from 10° to 45°, a space between the adjacent lugs 4 can be opened. In this way, soil draining ability can be improved and tractive force can be increased.