A detailed data aggregation apparatus holds detailed data of a plurality of events and a transcription and replenishment rule. In the rule, a plurality of common items, which are common to different events as a minimum unit of aggregation, are defined, and a transcription instruction (for instructing to transcribe a value corresponding to an event definition item to a value corresponding to the common item) and a replenishment instruction (for instructing to replenish a value to be replenished as the value corresponding to the common item) are described, associated with each common item for each event. Regarding the held detailed data, transcribed/replenished detailed data including values corresponding to the common items is created from the respective detailed data according to the transcription instruction or replenishment instruction. The apparatus aggregates the created data in a unit of predetermined common item specified as a unit of aggregation or in a unit of combination of predetermined common items.