A blood purification system comprising: a blood purification apparatus that gives blood purification treatment to a patient; a managing apparatus that communicates 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 unit that stores the information on the blood purification treatment as a history for each treatment session in a time course with progress of the treatment; and a display unit provided to the blood purification apparatus or to the managing apparatus and that displays the information on the blood purification treatment, characterized in that the blood purification system further includes an extracting unit that searches for and extracts any history satisfying a predetermined condition from among the histories stored in the storage unit; an excluding unit that excludes any of the histories stored in the storage unit from an object of search performed by the extracting unit; and a display control unit that controls various pieces of information based on the history extracted by the extracting unit to be displayed on the display unit, wherein the histories each include a particular incident related to the patient's behavior or the patient's condition having occurred unsteadily in the blood purification treatment, and wherein the extracting unit is capable of extracting the particular incident by searching the histories stored in the storage unit except the history excluded by the excluding unit; the blood purification system includes a calculating unit that calculates a time when the particular incident extracted by the extracting unit occurs a predetermined or more number of times as a frequent-occurrence time slot; and the display control unit controls the frequent-occurrence time slot calculated by the calculating unit to be displayed on the display unit during a current session of blood purification treatment. a blood purification apparatus that gives blood purification treatment to a patient; a managing apparatus that communicates 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 unit that stores the information on the blood purification treatment as a history for each treatment session in a time course with progress of the treatment; and a display unit provided to the blood purification apparatus or to the managing apparatus and that displays the information on the blood purification treatment, characterized in that the blood purification system further includes an extracting unit that searches for and extracts any history satisfying a predetermined condition from among the histories stored in the storage unit; an excluding unit that excludes any of the histories stored in the storage unit from an object of search performed by the extracting unit; and a display control unit that controls various pieces of information based on the history extracted by the extracting unit to be displayed on the display unit, wherein the histories each include a particular incident related to the patient's behavior or the patient's condition having occurred unsteadily in the blood purification treatment, and wherein the extracting unit is capable of extracting the particular incident by searching the histories stored in the storage unit except the history excluded by the excluding unit; the blood purification system includes a calculating unit that calculates a time when the particular incident extracted by the extracting unit occurs a predetermined or more number of times as a frequent-occurrence time slot; and the display control unit controls the frequent-occurrence time slot calculated by the calculating unit to be displayed on the display unit during a current session of blood purification treatment. an extracting unit that searches for and extracts any history satisfying a predetermined condition from among the histories stored in the storage unit; an excluding unit that excludes any of the histories stored in the storage unit from an object of search performed by the extracting unit; and a display control unit that controls various pieces of information based on the history extracted by the extracting unit to be displayed on the display unit, wherein the histories each include a particular incident related to the patient's behavior or the patient's condition having occurred unsteadily in the blood purification treatment, and wherein the extracting unit is capable of extracting the particular incident by searching the histories stored in the storage unit except the history excluded by the excluding unit; the blood purification system includes a calculating unit that calculates a time when the particular incident extracted by the extracting unit occurs a predetermined or more number of times as a frequent-occurrence time slot; and the display control unit controls the frequent-occurrence time slot calculated by the calculating unit to be displayed on the display unit during a current session of blood purification treatment.