An operating method of a data storage device including nonvolatile memory devices includes making a victim block list for victim blocks for which a merge operation is to be performed and copying valid pages of the victim bocks to a merge block. The method also includes determining whether there is a victim block which has an erase-held valid page selectively erasing the victim blocks included in the victim block list, according to which victim blocks have an erase-held page, and updating the victim block list according to which victim blocks are erased.