To provide an outrigger device capable of supporting a vehicle body by surely holding a rod end part of a cylinder without the possibility of damage of a slide supporting mechanism part, even if a jack cylinder is elongated in a state of a float moved to a storage position.

This outrigger device is constituted by providing an outrigger inner box to be expandable in the vehicle body, providing the jack cylinder 25 with a rod side end part directed downward at a distal end part of the inner box, providing the float 30 at the rod end part of the cylinder 25, providing a first spherical seat 34 abutted by the rod end part in a center part of the float 30, providing a slide supporting mechanism 50 for slidably supporting the float 30 between a use position where the first spherical seat 34 is located on a lower side of the rod end part and the storage position where a float end part side is located on the lower side of the rod end part in an upper part of the float 30, and providing a second spherical seat 38 abutted by the rod end part of the jack cylinder 25 in a state of the float 30 moved to the storage position on an upper surface on the end part side of the float 30.