A blood purification system comprising: a blood purification apparatus configured to give blood purification treatment to a patient; a managing apparatus configured to communicate with the blood purification apparatus in such a manner as to transmit and receive information on the blood purification treatment to and from the blood purification apparatus, the managing apparatus including a storage device configured to store the information on the blood purification treatment in a time course with progress of the treatment and to accumulate the information as a history for each treatment session; and a display provided to the blood purification apparatus or to the managing apparatus and being capable of displaying the information on the blood purification treatment, wherein the history includes a particular parameter related to the treatment and that changes with time during the blood purification treatment, and characterized in that the blood purification system further includes an extracting device configured to search the histories accumulated in the storage device and to extract, as an approximate history, a history including the particular parameter approximate to the particular parameter observed at a current time in a current session of blood purification treatment or a history including the particular parameter exhibiting a transition approximate to a transition of the particular parameter observed until the current time in the current session of blood purification treatment; an estimating device that estimates a transition of the particular parameter to be observed after the current time in the current session of blood purification treatment from the approximate history extracted by the extracting device; and a display control device configured to displaying the transition of the particular parameter estimated by the estimating device and the transition of the particular parameter observed in the current session of blood purification treatment simultaneously on the display. a blood purification apparatus configured to give blood purification treatment to a patient; a managing apparatus configured to communicate with the blood purification apparatus in such a manner as to transmit and receive information on the blood purification treatment to and from the blood purification apparatus, the managing apparatus including a storage device configured to store the information on the blood purification treatment in a time course with progress of the treatment and to accumulate the information as a history for each treatment session; and a display provided to the blood purification apparatus or to the managing apparatus and being capable of displaying the information on the blood purification treatment, wherein the history includes a particular parameter related to the treatment and that changes with time during the blood purification treatment, and characterized in that the blood purification system further includes an extracting device configured to search the histories accumulated in the storage device and to extract, as an approximate history, a history including the particular parameter approximate to the particular parameter observed at a current time in a current session of blood purification treatment or a history including the particular parameter exhibiting a transition approximate to a transition of the particular parameter observed until the current time in the current session of blood purification treatment; an estimating device that estimates a transition of the particular parameter to be observed after the current time in the current session of blood purification treatment from the approximate history extracted by the extracting device; and a display control device configured to displaying the transition of the particular parameter estimated by the estimating device and the transition of the particular parameter observed in the current session of blood purification treatment simultaneously on the display. an extracting device configured to search the histories accumulated in the storage device and to extract, as an approximate history, a history including the particular parameter approximate to the particular parameter observed at a current time in a current session of blood purification treatment or a history including the particular parameter exhibiting a transition approximate to a transition of the particular parameter observed until the current time in the current session of blood purification treatment; an estimating device that estimates a transition of the particular parameter to be observed after the current time in the current session of blood purification treatment from the approximate history extracted by the extracting device; and a display control device configured to displaying the transition of the particular parameter estimated by the estimating device and the transition of the particular parameter observed in the current session of blood purification treatment simultaneously on the display.