1. A business process tracking apparatus for tracking a business process which is a flow of a business that is executed with spreading across different business systems, the apparatus comprising: means for storing business data being treated in a business in each business system and business process definition information defining relative information between respective business data; event data collection means for collecting event data which is information showing an execution status of an application which executes each of businesses extracted in the business system; event relation means for grouping the collected event data in units of business data on the basis of the business process definition information, and relating business data collected as event data; event management data storage means for storing the related business data; and output means for outputting relation between business data in a tree form by retrieving the event management data storage means on the basis of inputted retrieval conditions.