1. A design data merging apparatus comprising: a computer; and a memory storing instructions executed by the computer for: a merging determining unit that determines, for a plurality of design data of which each has product name information and has a same identifier for uniquely identifying a product, whether the product name information given to the plurality of design data are the same; and a merged data creating unit that merges the plurality of design data when it is determined by the merging determining unit that the product name information given to the plurality of design data are the same, and creates merged data obtained by merging a plurality of design data.