A particle beam treatment device in which, when an irradiation target is partitioned along a depth direction thereof into a plurality of slices and a particle beam formed for each of the slices is radiated thereto in a depth order, an energy of the particle beam to be emitted from an accelerator is set for every slice group including two or more adjacent ones of the slices, and an attenuation amount is set for each slice in the slice group, the particle beam treatment device comprising: - a variable range shifter comprising a transmissive plate that is adapted to adjust the attenuation amount by changing a thickness of its transmissive plate through which the particle beam is transmitted; - an irradiation nozzle that has a scanning electromagnet and that is adapted to make a forming of the particle beam to be adjusted in the attenuation amount, according to each of the slices; - a four-pole electromagnet that is placed between the variable range shifter and the irradiation nozzle, and that is adapted to operate so as to converge the particle beam having been spread by the transmissive plate; and - a control unit that is adapted to determine set values of the accelerator and the variable range shifter, and that is adapted to control an amount of magnetic excitation of the four-pole electromagnet according to the set values; characterized in that: for said every slice group, the control unit is adapted to set higher the energy to be emitted from the accelerator than an energy corresponding to the slice at a deepest location in the slice group and set a transmissive plate having a predetermined thickness for the slice at the deepest location; and wherein, with respect to the thickness of the transmissive plate to be set for said every slice group, the thickness set for the slice group at a deep location is larger than or equal to the thickness set for the slice group at a shallow location, and the thickness set for the slice group at a deepest location is thicker than the thickness set for the slice group at a shallowest location. - a variable range shifter comprising a transmissive plate that is adapted to adjust the attenuation amount by changing a thickness of its transmissive plate through which the particle beam is transmitted; - an irradiation nozzle that has a scanning electromagnet and that is adapted to make a forming of the particle beam to be adjusted in the attenuation amount, according to each of the slices; - a four-pole electromagnet that is placed between the variable range shifter and the irradiation nozzle, and that is adapted to operate so as to converge the particle beam having been spread by the transmissive plate; and - a control unit that is adapted to determine set values of the accelerator and the variable range shifter, and that is adapted to control an amount of magnetic excitation of the four-pole electromagnet according to the set values; for said every slice group, the control unit is adapted to set higher the energy to be emitted from the accelerator than an energy corresponding to the slice at a deepest location in the slice group and set a transmissive plate having a predetermined thickness for the slice at the deepest location; and wherein, with respect to the thickness of the transmissive plate to be set for said every slice group, the thickness set for the slice group at a deep location is larger than or equal to the thickness set for the slice group at a shallow location, and the thickness set for the slice group at a deepest location is thicker than the thickness set for the slice group at a shallowest location.