1. A work transfer system including a plurality of work transfer units which connect a plurality of loading places to a plurality of unloading places, the system comprising: a layout information database which stores layout information representing a layout of the plurality of work transfer units; and route setting means for setting, based on the layout information, a route of the work transfer units to pass a work between a planned loading place and a planned unloading place which are required to transfer the work in the plurality of loading places and the plurality of unloading places, wherein said route setting means comprising: candidate setting means for setting a plurality of candidates of the route between the planned loading place and the planned unloading place; and route selection means for selecting, based on a predetermined condition, one route from the plurality of candidates of the route set by said candidate setting means.