A work vehicle comprising: an engine; a rotational speed sensor that detects a rotational speed of the engine; a hydraulic pump driven by the engine, a hydraulic motor driven with hydraulic oil discharged from the hydraulic pump to drive wheels (113, 123), and an HST circuit in which the hydraulic pump and the hydraulic motor are connected to each other in a form of a closed circuit; an accelerator pedal and an accelerator pedal operation amount detector that detects a pedal operation amount by which the accelerator pedal is operated; a reducing agent sensor (18, 19) that detects a state of a reducing agent used to clean exhaust gas from the engine; an engine controller that restricts the rotational speed of the engine based on an output from the reducing agent sensor (18, 19); and a vehicle controller that is connected to the reducing agent sensor (18, 19), the rotational speed sensor, and the accelerator pedal operation amount detector and controls the hydraulic pump or the hydraulic motor, characterized in that in a case where an output value from the reducing agent sensor (18, 19) does not satisfy a predetermined condition, the engine controller is configured to restrict the engine rotational speed to a low idle-speed, and in a state in which the engine rotational speed is restricted to a low idle-speed, the engine rotational speed outputted by the rotational speed sensor is lower than a predetermined speed, and the pedal operation amount outputted by the accelerator pedal operation amount detector is greater than a predetermined threshold, the vehicle controller determines that the engine restrictor has restricted the rotational speed of the engine and changes a tilting angle of the hydraulic pump or the hydraulic motor independently of the rotational speed of the engine to the tilting angle associated with minimum travel drive force necessary for self-travel of the work vehicle. an engine; a rotational speed sensor that detects a rotational speed of the engine; a hydraulic pump driven by the engine, a hydraulic motor driven with hydraulic oil discharged from the hydraulic pump to drive wheels (113, 123), and an HST circuit in which the hydraulic pump and the hydraulic motor are connected to each other in a form of a closed circuit; an accelerator pedal and an accelerator pedal operation amount detector that detects a pedal operation amount by which the accelerator pedal is operated; a reducing agent sensor (18, 19) that detects a state of a reducing agent used to clean exhaust gas from the engine; an engine controller that restricts the rotational speed of the engine based on an output from the reducing agent sensor (18, 19); and a vehicle controller that is connected to the reducing agent sensor (18, 19), the rotational speed sensor, and the accelerator pedal operation amount detector and controls the hydraulic pump or the hydraulic motor, characterized in that in a case where an output value from the reducing agent sensor (18, 19) does not satisfy a predetermined condition, the engine controller is configured to restrict the engine rotational speed to a low idle-speed, and in a state in which the engine rotational speed is restricted to a low idle-speed, the engine rotational speed outputted by the rotational speed sensor is lower than a predetermined speed, and the pedal operation amount outputted by the accelerator pedal operation amount detector is greater than a predetermined threshold, the vehicle controller determines that the engine restrictor has restricted the rotational speed of the engine and changes a tilting angle of the hydraulic pump or the hydraulic motor independently of the rotational speed of the engine to the tilting angle associated with minimum travel drive force necessary for self-travel of the work vehicle.