A route search program for finding a guidance travel route to be targeted by a work vehicle travelling in a work field, the route search program causing a computer to achieve: a search area setting function of setting, as a search area, a fan shaped area spreading in a travel direction from an own vehicle reference point which is a predetermined reference point of the work vehicle; a positional relationship calculation function of calculating positional relationships among a plurality of travel route candidates, an own position of the work vehicle and the search area, the plurality of travel route candidates being read from a travel route storing unit storing a plurality of travel routes in the work field, the own position being calculated based on positioning data sent from a positioning module, wherein perpendicular lines passing through the own vehicle reference point toward the plurality of travel route candidates are obtained, each perpendicular line defining a shortest distance between the own vehicle reference point and a travel route; a guidance route selection function of selecting, as the guidance travel route to be targeted by the work vehicle, a travel route candidate determined as closest to the own vehicle reference point in the search area, based on the positional relationships, from among the plurality of travel route candidates; wherein, when it is determined that the own vehicle reference point lies on a travel route candidate, such a travel route candidate is selected as the guidance travel route; wherein, when it is determined that the own vehicle reference point does not lie on a travel route candidate, it is determined whether an end point of an actual travel route portion of a travel route candidate is within a circle area of a search distance, wherein if the end point of the actual travel route portion of the travel route candidate is within the circle area of the search distance, it is determined whether an angle between a straight line joining the end point and the own vehicle reference point and a travel direction of a vehicle body falls within a predetermined range, wherein when the angle between the straight line joining the end point and the own vehicle reference point and the travel direction of the vehicle body falls within a predetermined range, a node between a side (Se) of the search area and a travel route candidate is calculated, and wherein when the node lies on an actual travel route portion of the travel route candidate, such a travel route candidate is selected as the guidance travel route; and a deviation calculation function of calculating a deviation between the guidance travel route and the own position. a search area setting function of setting, as a search area, a fan shaped area spreading in a travel direction from an own vehicle reference point which is a predetermined reference point of the work vehicle; a positional relationship calculation function of calculating positional relationships among a plurality of travel route candidates, an own position of the work vehicle and the search area, the plurality of travel route candidates being read from a travel route storing unit storing a plurality of travel routes in the work field, the own position being calculated based on positioning data sent from a positioning module, wherein perpendicular lines passing through the own vehicle reference point toward the plurality of travel route candidates are obtained, each perpendicular line defining a shortest distance between the own vehicle reference point and a travel route; a guidance route selection function of selecting, as the guidance travel route to be targeted by the work vehicle, a travel route candidate determined as closest to the own vehicle reference point in the search area, based on the positional relationships, from among the plurality of travel route candidates; wherein, when it is determined that the own vehicle reference point lies on a travel route candidate, such a travel route candidate is selected as the guidance travel route; wherein, when it is determined that the own vehicle reference point does not lie on a travel route candidate, it is determined whether an end point of an actual travel route portion of a travel route candidate is within a circle area of a search distance, wherein if the end point of the actual travel route portion of the travel route candidate is within the circle area of the search distance, it is determined whether an angle between a straight line joining the end point and the own vehicle reference point and a travel direction of a vehicle body falls within a predetermined range, wherein when the angle between the straight line joining the end point and the own vehicle reference point and the travel direction of the vehicle body falls within a predetermined range, a node between a side (Se) of the search area and a travel route candidate is calculated, and wherein when the node lies on an actual travel route portion of the travel route candidate, such a travel route candidate is selected as the guidance travel route; and a deviation calculation function of calculating a deviation between the guidance travel route and the own position.