Data searching apparatus to speed up searching time. This apparatus searches search target items associated with the specified relation items. When a group of search target items is associated with a same group of relation items, an upper item is defined to both of the groups of search target items and relation items. The relation between the upper item and relation items are recorded on first data, whereas the relation between the upper item and search target items are recorded on second data. The relations between the relation items and search items which are not associated with the upper items are recorded in third data. When part of or all of the specified relation items is contained in the first data, the first data, at least the second data is searched, and when no specified relation item is contained on the first data, only the third data is searched.