A history information anonymization method is provided that includes associating each of a plurality of pieces of history information collected from a plurality of TVs in a current cycle with a temporary ID associated with a TV at a collection destination. The method also includes getting together a plurality of IDs into a plurality of groups such that for the IDs in each group, contents of history information associated in the current cycle and in a past cycle are identical. The method further includes judging whether each of the plurality of groups satisfies anonymity, and changing only some of the plurality of temporary IDs associated with the plurality of TVs, when it is judged that any of the plurality of groups does not satisfy anonymity.