To solve problems in a conventional working vehicle wherein when front wheels are positioned at recessed parts and front and rear rollers and rear wheels are positioned at projected parts when four jacks with rollers are brought into contact with the ground and working is performed while moving a vehicle, the front wheels may be floated and since the front wheels are those for laterally steering the working vehicle, the steering of the working vehicle becomes impossible.

A work machine is mounted on the vehicle, and outriggers 4 having ground-contact plates 5 at their lower ends and supporting the working vehicle on the ground are disposed at the front right and left sides and the rear right and left sides of the vehicle 1. Rollers 6 in place of the ground-contact plates 5 can be disposed for the outriggers 4b disposed on the rear side. When the working vehicle is stopped and performs operations, the ground-contact plates 5 of the front and rear four outriggers 4 are brought into contact with the ground to support the working vehicle. When the working vehicle performs operations while traveling, the rollers 6 are disposed at the lower ends of the outriggers 4b, and only the outriggers 4b are extended in such a range that the wheels are not floated so that the working vehicle 1 can travel while supporting it on the ground by the rollers 6.