Control device and a control program of the work vehicle

A traveling control device and a traveling control program for a work vehicle or a control device and a control program for the work vehicle capable of fixing a control amount to a specified value since variation in control amount (speed ratio) due to the effect of the vibration of a vehicle body is less even if an operation device with shorter operation stroke is adopted and also capable of providing a control amount according to the feeling of an operator even when fine-adjustment is performed by increasing or decreasing the operation stroke. When an operation lever device is operated from a point on a first line (L11) in the direction for increasing the operation stroke and decreasing the speed ratio, the speed ratio is calculated according to the first line. When the operation lever device is operated from a point on a second line (L12) in the direction for reducing the operation stroke and increasing the speed ratio, the speed ratio is calculated according to the second line. When the operation lever is operated from the point on the first line in the direction for decreasing the operation stroke and increasing the speed ratio or from the point on the second line in the direction for increasing the operation stroke and decreasing the speed ratio, the speed ratio is calculated according to third lines (L131)-(L134).