1. A business process tracking apparatus for tracking a business process which is a flow of a plurality of businesses that are executed in a plurality of business systems, the apparatus comprising: means for storing a plurality of business data used in the plurality of business systems and business process definition information defining a relation between the plurality of business data by using relative properties; event data collection means for collecting event data from the plurality of business systems, the event data extracted in the plurality of business systems comprising the relative properties and information showing an execution status of each of a plurality of applications, the plurality of applications executing the plurality of businesses; event relation means for grouping the collected event data having relative properties in common based upon the stored business process definition information and the relative properties included in the collected event data from the plurality of business systems, and relating the grouped event data among the plurality of business systems based upon the plurality of business data; event management data storage means for storing the related event data; and output means for outputting the related event data in a tree form by retrieving the event data from the event management data storage means based upon input retrieval conditions.