A speed changing structure for a work vehicle, comprising a travel speed changing device having a plurality of speed change positions, a manually operated speed changing lever (63), control means (64) for controlling the travel speed changing device, and a manually operable operating part (65) provided to the speed changing lever (63), wherein the control means (64) has a first speed changing mode for operating the travel speed changing device in single steps so as to follow the operation of the speed changing lever (63), and a second speed changing mode for operating the travel speed changing device without passing through intermediate speed change positions to a speed change position that corresponds to the operating position after the speed changing lever (63) has been moved from the speed change position that corresponds to the operating position prior to the speed changing lever (63) being operated; and the control means (64) operates the travel speed changing device in the first speed changing mode when the operating part (65) is not operated and the speed changing lever (63) is operated, and operates the travel speed changing device in the second speed changing mode when the operating part (65) is operated and the speed changing lever is operated.