PROBLEM TO BE SOLVED: To provide a prime mover structure of a working vehicle superior in cooling efficiency of a radiator and the like.SOLUTION: The problem is solved by arranging a radiator (60), for cooling coolant of an engine (20) between the engine (20) and a filter (14), in an engine room (8), arranging a fan (40), for sucking outside air through the filter (14), between the engine (20) and the radiator (60), and arranging a hydraulic continuously variable transmission (30), for transmitting rotation of the engine (20) to the fan (40), at an upper portion of the engine (20).