Provided are an engine 111, a generator-motor 113, a clutch 112 connecting/disconnecting power therebetween, a battery 115, and a loading pump 117 for driving a fork 118. The generator-motor 113 is set either in a generator mode or in a motor mode. When a cargo handling load (detected by a loading lever position sensor 145 and the like) is smaller than a predetermined value, the clutch 112 is set to a disconnection state, the engine 111 is stopped or idled, and the loading pump 117 is driven by the generator-motor 113 in the motor mode. When the load is increased to the predetermined value or more during cargo handling work in a state where the clutch 112 is released, an increase of the number of revolution of the engine is started while an output of the generator-motor 113 is being increased. When the number of revolution of the engine 111 is made equal to the number of revolution of the generator-motor 113, the clutch 112 is set to a connected state, and the loading pump 117 is driven by the engine 111.