PROBLEM TO BE SOLVED: To obtain a control amount (speed ratio) corresponding to the feeling of an operator while suppressing a change in the control amount (speed ratio) due to an effect of vehicle vibration or the like, even if an operation device with a short operation stroke range is used.SOLUTION: In a controller, a first line L11 in which a speed ratio is reduced according to a change in operation stroke, a second line L12 obtained by adding hysteresis to the first line L11 and in which the speed ratio is increased according to the change in operation stroke, and third lines L131, L132, L133 and L134 where the speed ratio is changed according to the change in operation stroke and having a small change in the speed ratio relative to the operation stroke, are set. When an operation lever is operated in a direction where the operation stroke decreases from a point on the first line and the speed ratio increases, or a direction where the operation stroke increases from a point on the second line and the speed ratio increases, a speed ratio is calculated in accordance with the third line.