A travel route determination device configured to determine a travel route for a work vehicle that travels while working in a work site, the device comprising: an area setting unit configured to set an area to be worked by the work vehicle in the work site; a route managing unit configured to calculate a travel route element set and to store it in a readable format, wherein the travel route element set is an aggregate of multiple travel route elements constituting a travel route covering the area to be worked and is a parallel line set constituted by parallel lines that are parallel to each other and divide the area to be worked into rectangular shapes, wherein movement from one end of one travel route element to one end of another travel route element is executed through U-turn travel by the work vehicle; a first route element selecting unit configured to calculate a selection order for the travel route elements of an overall travel route on the basis of a basic priority rule, before the work travel by the work vehicle; a second route element selecting unit configured to, while the work vehicle carries out work travel based on the selection order calculated by the first route element selecting unit, extract an untraveled travel route element from the travel route element set as a recalculated travel route element, and to recalculate a selection order for the recalculated travel route element on the basis of a cost evaluation rule, a cost evaluated by the cost evaluation rule depending on a travel distance of the U-turn travel; and a route setting unit configured to correct the selection order calculated by the first route element selecting unit with the selection order calculated by the second route element selecting unit. an area setting unit configured to set an area to be worked by the work vehicle in the work site; a route managing unit configured to calculate a travel route element set and to store it in a readable format, wherein the travel route element set is an aggregate of multiple travel route elements constituting a travel route covering the area to be worked and is a parallel line set constituted by parallel lines that are parallel to each other and divide the area to be worked into rectangular shapes, wherein movement from one end of one travel route element to one end of another travel route element is executed through U-turn travel by the work vehicle; a first route element selecting unit configured to calculate a selection order for the travel route elements of an overall travel route on the basis of a basic priority rule, before the work travel by the work vehicle; a second route element selecting unit configured to, while the work vehicle carries out work travel based on the selection order calculated by the first route element selecting unit, extract an untraveled travel route element from the travel route element set as a recalculated travel route element, and to recalculate a selection order for the recalculated travel route element on the basis of a cost evaluation rule, a cost evaluated by the cost evaluation rule depending on a travel distance of the U-turn travel; and a route setting unit configured to correct the selection order calculated by the first route element selecting unit with the selection order calculated by the second route element selecting unit.