Abstract: A particle therapy device is provided. The particle therapy device includes a gantry, which is rotatable about an axial axis of rotation and surrounds a treatment chamber with a floor that has at least one movable plate, a treatment table being positionable inside the treatment chamber. To make it possible for a patient, supported on the treatment table, to be irradiated from below as well, the plate is movable horizontally out of the treatment chamber in a transverse direction that extends perpendicular to the axial direction.