1. A merging apparatus comprising: a first database that store therein, as records, each of attribute values that is classified under one or a plurality of attributes and that is associated with each other, in which a plurality of attributes including a key attribute that is set in advance as a key for merging is set; a second database that store therein, as records, each of the attribute values, in which one or a plurality of attributes excluding the key attribute is set; an extracting unit that checks the attribute that is set in the first database against the attribute that is set in the second database and extracts a common attribute that is set, in common, in both the first database and the second database; and a merging unit that merges the first database with the second database by determining whether attribute values classified under the common attribute that is extracted by the extracting unit match.