The present invention provides a highly reliable circulation apparatus which promptly detects an abnormal state of a status value related to blood flowing in a circulation circuit with no particular operation performed. Therefore, as an extracorporeal circulation mode starts, a user operates a pump first and waits until a flow rate is stabilized. Then, when the flow rate is stabilized, a predetermined value is added to or subtracted from the stabilized flow rate so as to set two threshold values which regulate an upper end and a lower end of a permissible state range. Since then, it is monitored whether or not the flow rate is within the permissible state range regulated by the threshold values, and when the flow rate deviates from the permissible state range, an alarm is issued for notification.
