The invention relates to a hadron therapy installation (1) that comprises a moving floor (8′, 8″) in the form of a deformable band guided in a guide structure (10). A lower segment (8′) can be pulled by the irradiation unit (5) from a lower docked position to a position in which it forms a substantially horizontal floor surface, when the irradiation unit (5) is in a first angular position (a). An upper segment (8″) can be pulled by the irradiation unit (5) from an upper docked position to a position in which it at least partially forms said substantially horizontal floor surface, when the irradiation unit (5) is in a second angular position (β). The lower segment (8′) and the upper segment (8″) are segments with a finite length. A counterweight (19) is connected to the free end of the upper segment (8″), so as to exert a traction force on the latter toward the upper docked position.
