To shortly form the whole length of a transmission case.

In a travelling vehicle for transmitting power to a front wheel by a hydraulic clutch type power transmission device 3 for transmitting power by pressing an engine driving side multiple disk 1 for transmitting driving force from an engine into contact with a driven side multiple disk 2 connected to the front wheel, a gear 53 is formed around the periphery of a rotary drum 52 on which the driven side multiple disk 2 of a hydraulic clutch is arranged, and a rotary sensor 6 for measuring the rotation of the gear 53 and a rotation lock mechanism 7 are attached to the gear 53 from the side surfaces of a transmission case.