A charged particle irradiation apparatus configured to perform a scan with a charged particle beam to irradiate an irradiation target spot by spot, the charged particle irradiation apparatus comprising: a collimator apparatus (100, 300) provided in an irradiation nozzle 50) configured to emit a charged particle beam to an irradiation target; and a collimator control unit configured to control the collimator apparatus, wherein the collimator apparatus comprises a collimator mechanism (102, 302) comprising one or more arm-shape collimators (110, 120, 310, 320) extending from a base part (106, 306), and a drive mechanism configured to move the collimator mechanism on a plane (YZ plane) perpendicular to a traveling direction (X-axis direction) of a charged particle beam, wherein each of the arm-shape collimators comprises a plurality of movable leaves that rotate independently of each other on the perpendicular plane (YZ plane), and wherein by moving the collimator mechanism and/or rotating the movable leaves so that the one or more arm-shape collimators are arranged along a shape of an edge of an irradiation target on the perpendicular plane (YZ plane), the collimator control unit causes the one or more arm-shape collimators to block a charged particle beam that would otherwise irradiate outside of the edge of the irradiation target, wherein (i) the plurality of movable leaves are connected to each other in series, or (ii) the plurality of movable leaves are connected to the base part and arranged adjacently in the traveling direction (X-axis direction). a collimator apparatus (100, 300) provided in an irradiation nozzle 50) configured to emit a charged particle beam to an irradiation target; and a collimator control unit configured to control the collimator apparatus, wherein the collimator apparatus comprises a collimator mechanism (102, 302) comprising one or more arm-shape collimators (110, 120, 310, 320) extending from a base part (106, 306), and a drive mechanism configured to move the collimator mechanism on a plane (YZ plane) perpendicular to a traveling direction (X-axis direction) of a charged particle beam, a collimator mechanism (102, 302) comprising one or more arm-shape collimators (110, 120, 310, 320) extending from a base part (106, 306), and a drive mechanism configured to move the collimator mechanism on a plane (YZ plane) perpendicular to a traveling direction (X-axis direction) of a charged particle beam, wherein each of the arm-shape collimators comprises a plurality of movable leaves that rotate independently of each other on the perpendicular plane (YZ plane), and wherein by moving the collimator mechanism and/or rotating the movable leaves so that the one or more arm-shape collimators are arranged along a shape of an edge of an irradiation target on the perpendicular plane (YZ plane), the collimator control unit causes the one or more arm-shape collimators to block a charged particle beam that would otherwise irradiate outside of the edge of the irradiation target, wherein (i) the plurality of movable leaves are connected to each other in series, or (ii) the plurality of movable leaves are connected to the base part and arranged adjacently in the traveling direction (X-axis direction).