A traction control apparatus for an all-wheel-drive construction vehicle, comprising: a vehicle speed estimator that estimates a vehicle speed, the vehicle speed estimator comprising a rotation speed detector (43FL, 43FR, 43CL, 43CR) that detects a rotation speed of each of wheels; and a driving-force controller that performs a driving-force control of the construction vehicle based on the estimated vehicle speed estimated by the vehicle speed estimator, the driving-force controller comprising a braking mechanism controller that controls a braking mechanism of the construction vehicle; characterized in that the braking mechanism controller calculates a slip ratio of each of the wheels based on the rotation speed detected by the rotation speed detector (43FL, 43FR, 43CL, 43CR) and controls the braking mechanism so that the calculated slip ratio converges to a predetermined target value; the vehicle speed estimator comprises a reference wheel-speed calculator that calculates a reference wheel-speed based on the rotation speed detected by the rotation speed detector (43FL, 43FR, 43CL, 43CR); the vehicle speed estimator comprises a reference speed calculator that calculates a reference speed by adding a value of integral of an acceleration and deceleration component of an acceleration acting in a travel direction of the construction vehicle to a previously estimated vehicle speed; the vehicle speed estimator estimates the vehicle speed of the construction vehicle based on the calculated reference wheel-speed and the calculated reference speed; and the traction control apparatus comprises a vehicle state determiner that determines whether or not the estimated vehicle speed of the construction vehicle estimated by the vehicle speed estimator and the driving-force control by the driving-force controller are balanced; and a driving-force control changer that changes a driving-force control by the driving-force controller when the vehicle state determiner determines that the estimated vehicle speed and the driving-force control are unbalanced; wherein the vehicle state determiner determines the estimated vehicle speed and the driving-force control to be unbalanced when the slip ratio calculated by the braking mechanism controller exceeds the target value and is kept at a predetermined threshold or more for a predetermined time or more; and wherein the vehicle state determiner determines the estimated vehicle speed and the driving-force control to be unbalanced when a braking control amount of the braking mechanism by the braking mechanism controller is kept at a predetermined threshold or more for a predetermined time or more. a vehicle speed estimator that estimates a vehicle speed, the vehicle speed estimator comprising a rotation speed detector (43FL, 43FR, 43CL, 43CR) that detects a rotation speed of each of wheels; and a driving-force controller that performs a driving-force control of the construction vehicle based on the estimated vehicle speed estimated by the vehicle speed estimator, the driving-force controller comprising a braking mechanism controller that controls a braking mechanism of the construction vehicle; characterized in that the braking mechanism controller calculates a slip ratio of each of the wheels based on the rotation speed detected by the rotation speed detector (43FL, 43FR, 43CL, 43CR) and controls the braking mechanism so that the calculated slip ratio converges to a predetermined target value; the vehicle speed estimator comprises a reference wheel-speed calculator that calculates a reference wheel-speed based on the rotation speed detected by the rotation speed detector (43FL, 43FR, 43CL, 43CR); the vehicle speed estimator comprises a reference speed calculator that calculates a reference speed by adding a value of integral of an acceleration and deceleration component of an acceleration acting in a travel direction of the construction vehicle to a previously estimated vehicle speed; the vehicle speed estimator estimates the vehicle speed of the construction vehicle based on the calculated reference wheel-speed and the calculated reference speed; and the traction control apparatus comprises a vehicle state determiner that determines whether or not the estimated vehicle speed of the construction vehicle estimated by the vehicle speed estimator and the driving-force control by the driving-force controller are balanced; and a driving-force control changer that changes a driving-force control by the driving-force controller when the vehicle state determiner determines that the estimated vehicle speed and the driving-force control are unbalanced; wherein the vehicle state determiner determines the estimated vehicle speed and the driving-force control to be unbalanced when the slip ratio calculated by the braking mechanism controller exceeds the target value and is kept at a predetermined threshold or more for a predetermined time or more; and wherein the vehicle state determiner determines the estimated vehicle speed and the driving-force control to be unbalanced when a braking control amount of the braking mechanism by the braking mechanism controller is kept at a predetermined threshold or more for a predetermined time or more.