To achieve compactness of a power transmission system, and facilitate the assembling of a power take-off means.

An engine 1 and a transmission for traveling 4 are integrated and mounted between a front wheel axle 45 and a rear wheel axle 47 in a car body 41, a rotation number synchronism type power take-off means 52 is provided on the output shaft side of the engine 1, and an output shaft 52a of the power take-off means 52 is connected to an attached device 54 fixed to a load-carrying platform 43. Since the engine 1, the transmission 4 for traveling, and the rotation number synchronism type power taking means 52 are intensively provided at a place, the whole power transmission system can be compacted, and as it can be easily mounted between the front wheel axle 45 and the rear wheel axle 47, weight distribution to front wheels 44 and rear wheels 46 can be set at the optimum value. In addition, as the engine 1 is disposed at the front part of the load-carrying platform 43, the power take-off means 52 to connect the engine 1 to the attached device 54 installed on the load-carrying platform 43 can be easily assembled.