A charged-particle beam irradiation device, which irradiates an irradiation target with a charged-particle beam, includes a transport line that transports the charged-particle beam and a rotating gantry that is rotatable about a rotation axis. The transport line includes an inclination portion making the charged-particle beam travel so that the charged-particle beam is inclined to be separated from the rotation axis, and is formed to turn the charged-particle beam in a rotation direction of the rotation axis and to bend the charged-particle beam, which has turned in the rotation direction, toward the rotation axis. The rotating gantry is formed of a cylindrical portion that receives the irradiation target and supports the transport line. The inclination portion is disposed in the cylindrical portion of the rotating gantry. The charged-particle beam irradiation device further includes blocking members that block radiation emitted from the transport line disposed in the cylindrical portion.