In an apparatus for controlling operation of an autonomously navigating utility vehicle travelling about a working area delineated by a boundary wire, the working area including a narrow area and a broad area, there are provided with a magnetic field strength detector, a travel controlling unit controlling the vehicle to turn and travel straight forward every time the vehicle reaches the boundary wire based on the magnetic field strength, and a narrow area discriminating unit discriminating that the vehicle travels in the narrow area when the magnetic field strength is kept to be greater than a threshold value predefined based on a minimum value of the magnetic field strength in the narrow area from a first turn to a second turn of the vehicle, or for a predetermined time period after the first turn.
