A traction control device of a construction machine comprising a braking mechanism (5, 6) provided to each of wheels and a differential adjusting mechanism (1 CA) for adjusting a differential between front and rear wheels, the traction control device controlling the braking mechanism (5, 6) and the differential adjusting mechanism, the traction control device comprising: a rotation speed detector that detects a rotation speed of each of the wheels; a control-start determiner that determines whether or not to control the braking mechanism (5, 6) and the differential adjusting mechanism based on the detected rotation speed of each of the wheels; a braking mechanism controller that controls the braking mechanism (5, 6) based on a result of the determination of the control-start determiner; and a differential adjusting mechanism controller that controls the differential adjusting mechanism (1 CA) based on the result of the determination of the control-start determiner, wherein the control-start determiner comprises: a right-left-wheel rotation speed difference calculating section that calculates a rotation speed difference between right and left wheels; a front-rear-wheel rotation speed difference calculating section that calculates a rotation speed difference between the front and rear wheels; and a control-start determining section that determines whether or not to start controlling at least one of the braking mechanism (5, 6) and the differential adjusting mechanism when at least one of the rotation speed differences between the right and left wheels and between the front and rear wheels reaches or exceeds a pre-stored predetermined threshold, wherein the control-start determining section determines to start controlling the braking mechanism (5, 6) and the differential adjusting mechanism when the rotation speed difference between the right and left wheels reaches or exceeds the right-left-wheel threshold, and determines to start controlling the differential adjusting mechanism when the rotation speed difference between the front and rear wheels reaches or exceeds the front-rear-wheel threshold. a rotation speed detector that detects a rotation speed of each of the wheels; a control-start determiner that determines whether or not to control the braking mechanism (5, 6) and the differential adjusting mechanism based on the detected rotation speed of each of the wheels; a braking mechanism controller that controls the braking mechanism (5, 6) based on a result of the determination of the control-start determiner; and a differential adjusting mechanism controller that controls the differential adjusting mechanism (1 CA) based on the result of the determination of the control-start determiner, wherein a right-left-wheel rotation speed difference calculating section that calculates a rotation speed difference between right and left wheels; a front-rear-wheel rotation speed difference calculating section that calculates a rotation speed difference between the front and rear wheels; and a control-start determining section that determines whether or not to start controlling at least one of the braking mechanism (5, 6) and the differential adjusting mechanism when at least one of the rotation speed differences between the right and left wheels and between the front and rear wheels reaches or exceeds a pre-stored predetermined threshold, wherein