A travel route generating device for a work vehicle includes a cell memory to store cell information with respect to cells obtained by dividing a topographical map of a work field in which the work vehicle works. A travel probability memory is to store a travel probability with respect to each of the cells. The travel probability includes a left-turn travel probability, a straight travel probability, and a right-turn travel probability in each of the cells. Circuitry is configured to determine a travel direction in each of the cells based on the travel probability of each of the cells. The work vehicle is configured to travel through each of the cells in the travel direction. The circuitry is configured to change the travel probability with respect to affected cells affected by moving the work vehicle through each of the cells.