A charged particle beam irradiation apparatus includes: a transport line configured to transport a charged particle beam; and a rotating gantry rotatable around a rotation axis, wherein the transport line has an inclined section configured to make the charged particle beam advancing in a direction of the rotation axis advance to be inclined so as to become more distant from the rotation axis, and is formed so as to turn the charged particle beam advanced in the inclined section to a rotational direction of the rotation axis and bend the charged particle beam turned to the rotational direction to the rotation axis side, the rotating gantry is formed of a tubular body which can accommodate an irradiated body and supports the transport line, and the inclined section is disposed to pass through the inside of the tubular body of the rotating gantry.