A similarity calculation apparatus according to the present invention includes: a name acquisition unit configured to acquire a first group name to which each word belonging to a first synonym group belongs and a second group name to which each word belonging to a second synonym group belongs; a name set generation unit configured to generate a first group name set and a second group name set; and a similarity calculation unit configured to calculate similarity between the first group name set and the second group name set. Therefore, even when a plurality of synonym groups are created, terms can be effectively unified.