A radiation-irradiation device includes a leg unit, a radiation source unit, an arm unit, a body unit, and a raising/lowering mechanism. The arm unit includes a first arm connected to the radiation source unit, a second arm, a first rotational moving portion that connects the first arm to the second arm so as to allow the first arm and second arm to be rotationally movable relative to each other, and a second rotational moving portion that connects the second arm to the raising/lowering mechanism so as to allow the second arm to be rotationally movable relative to the raising/lowering mechanism. The rotation of the second arm from an initial rotational movement position is regulated by the body unit in a case in which the arm unit is positioned at a position other than a first position where the arm unit is raised or lowered by the raising/lowering mechanism.