To provide a traveling working vehicle pivotal turn device that enables a QT device to be automatically switched on by operation of a drive control lever.
This device is provided with a drive control lever 55 for switching four-wheel drive to rear-wheel drive and vice versa, a detection means for detecting more than a predetermined value of the turning angle of front wheels 4a, and a front- wheel speed increasing device which increases the speed of the front wheels 4a relative to that of the rear wheels according to the detection means; the device is also provided with a changeover switch 9, which can be switched selectively to either a state in which right and left rear-wheel brakes 3 can be braked independently or a turning angle controlling operation state in which the brake 3 for the rear wheel that turns the body is operated as the turning angle of the front wheels 4a exceeds the predetermined value, and a first front-wheel speed increasing changeover switch 57 is connected in series with the detection means to operate the front wheel speed increasing device, whereas a second front-wheel speed increasing switch 59 operated by the switching of a traveling system control lever such as the drive control lever 55 is connected in parallel with the first front-wheel speed increasing changeover switch 57, so that the front wheel speed increasing device is operated by the operation of either the first 57 or second 59 switch.