Range shifter and particle radiotherapy device

A range shifter that outputs a particle beam incident thereto while attenuating energy of the particle beam, comprising:

• a transmissive plate whose thickness has been adjusted depending on a setup value of an amount of the energy to be attenuated;
• and
• a holder portion that holds the transmissive plate;
• wherein the thickness of the transmissive plate is adjusted to be a thickness equivalent to an attenuation amount lower than the setup value by a predetermined rate thereof;
• and
• wherein a superimposing mechanism capable of releasably superimposing an adjustment sheet over the transmissive plate, is provided to at least one of the transmissive plate and the holder portion, said adjustment sheet being adjusted to have a thickness equal to or less than a thickness equivalent to a two-fold attenuation amount of the predetermined rate.