Abstract: The present invention relates to a treatment device utilized in the freezing treatment method and its treatment planning device, and has an object to settle a freezing period·defrosting period according to a size of a treatment portion. A cryotherapy device comprises a gas supply-exhaust system 100, a control system 200 therefore and a freezing probe system 300. The gas supply-exhaust system 100 supplies a freezing gas and a defrosting gas to a probe 60 of the freezing probe system 300 to freeze and defrost the treatment portion surrounding the tip of the probe 60 by the Joule·Thomson effect. The control system 200 controls the gas supply-exhaust system 100 and makes treatment planning data for this control. The treatment planning data includes a freezing·defrosting sequence to determine the freezing period and the defrosting period. The determination of this sequence is performed by the computer in the control system 200.