A cargo handling controller includes a rotation speed setting unit, an engine control unit, a memory, a rotation speed detection unit, a deviation calculator, an assistance amount setting unit, and a generator-motor control unit. The deviation calculator calculates a deviation of a feedback control rotation speed, which is determined from a target engine rotation speed stored in the memory a predetermined time earlier, and an actual rotation speed of the generator-motor, which is detected by the rotation speed detection unit. The assistance amount setting unit obtains a generator-motor assistance amount in accordance with the deviation. The generator-motor control unit sends a drive signal that is in accordance with the generator-motor assistance amount to the generator-motor.