To assure safety and to protect the environment by operating the power transmission switch means of a PTO system to the disconnection side whether or not an operator performs operations when a working machine is raised to cause a vehicle body to travel at high speed.

The rotational power of an engine is made to branch from a drive shaft 40 into the transmission path 41 of a travel system and the transmission path 31 of a PTO system. A PTO clutch 32 is provided in the transmission path 31 of the PTO system and is turned on and off to transmit or shut off power to a PTO shaft 50. When the travel speed of a vehicle body exceeds a set speed, the PTO clutch 32 is disconnected by the command of a controller.