An inexpensive scanning irradiation device of a particle beam is obtained without using a rotating gantry. A first scanning electromagnet and a second scanning electromagnet, whose deflection surfaces of the particle beam are the same, and which bend the particle beam having an incident beam axis angle of approximately 45 degrees relative to a horizontal direction in reverse directions to each other; an electromagnet rotation driving mechanism which integrates the first and the second scanning electromagnets and rotates these scanning electromagnets around the incident beam axis; and a treatment bed are provided. The particle beam deflected by the first and the second scanning electromagnets can be obtained at a range of −45 degrees to +45 degrees in deflection angle from an incident beam axis direction.