A charged particle beam irradiation device includes a particle accelerator that accelerates charged particles and ejects a charged particle beam, a cylindrical outer shell part that is capable of rotating around a rotating axis, an irradiation unit that is capable of irradiating an irradiation target with the charged particle beam, the irradiation direction of which changes in accordance with the rotation of the outer shell part, and a beam transport line that transports the charged particle beam ejected from the particle accelerator to the irradiation unit. The particle accelerator and the beam transport line may be at least partially housed within the outer shell part.