An apparatus for controlling operation of a utility vehicle that is configured to detect a magnetic field generated during flow of electric current from an electric power supply through a boundary wire laid around a working area and being driven by a prime mover to run within the working area based on the detected magnetic field, having first and second magnetic sensors (36L, 36R) that are installed at lateral right and left positions symmetrical in a vehicle width direction of a body of the utility vehicle with respect to a vehicle center line extending in a forward-rearward direction and produce outputs proportional to strength of the magnetic field during flow of electric current through the boundary wire; and an electronic control unit having a microprocessor and a memory, wherein the microprocessor is configured to function as: a running control unit (44a1) configured to switch turning mode between a first turning mode and a second turning mode, each time predetermined conditions are satisfied, and to control operation of the prime mover such that the vehicle turns in accordance with the selected turning modes, characterized in that in the first turning mode the vehicle is controlled to turn without stopping in accordance with a desired turning radius and a first desired turning angle toward a side of one of the first and second magnetic sensors (36L, 36R) whose output indicates lower magnetic field strength (S18, S100 - S142), when the magnetic field strength of the boundary wire exceeds a certain value, and wherein an approach angle of the vehicle toward the boundary wire is calculated, and the first desired turning angle and the associated desired turning radius are respectively calculated to random values between minimum values and maximum values from the calculated approach angle (S18, S100 - S142), and in the second turning mode the vehicle is controlled to once stop the vehicle when a front end part of the body of the vehicle corresponding to at least one of the first and second magnetic sensors (36L, 36R) crosses over the boundary wire, and turn the vehicle with the front end of the body that crossed over the boundary wire as an outer wheel side (S28, S200 - S218) at a second desired turning angle which is randomly calculated. a running control unit (44a1) configured to switch turning mode between a first turning mode and a second turning mode, each time predetermined conditions are satisfied, and to control operation of the prime mover such that the vehicle turns in accordance with the selected turning modes, characterized in that in the first turning mode the vehicle is controlled to turn without stopping in accordance with a desired turning radius and a first desired turning angle toward a side of one of the first and second magnetic sensors (36L, 36R) whose output indicates lower magnetic field strength (S18, S100 - S142), when the magnetic field strength of the boundary wire exceeds a certain value, and wherein an approach angle of the vehicle toward the boundary wire is calculated, and the first desired turning angle and the associated desired turning radius are respectively calculated to random values between minimum values and maximum values from the calculated approach angle (S18, S100 - S142), and in the second turning mode the vehicle is controlled to once stop the vehicle when a front end part of the body of the vehicle corresponding to at least one of the first and second magnetic sensors (36L, 36R) crosses over the boundary wire, and turn the vehicle with the front end of the body that crossed over the boundary wire as an outer wheel side (S28, S200 - S218) at a second desired turning angle which is randomly calculated.