A pneumatic tire for off-road vehicles, which is highly durable under heavy load conditions is disclosed. The tire makes use as its breaker of a reinforcing element formed of material having a high cut resistant property such as steel or glass. The least possible number of those plies of a plurality of rubberized ply layers of a carcass body which extend from a crown portion of the tire through both side portions up to both bead members and which can substantially withstand internal pressure applied to the tire and external force subjected thereto is determined on the basis of a fundamental safety factor .xi. and which lies within a range of a correction safety factor .eta. which depends on the use and type of the tire and the depth of tread groove.