The present invention is the playback apparatus 400 for (i) mounting thereon the BD-ROM 200 in which a plurality of data groups and an application program that refers to each of the data groups are stored and (ii) playing back each of the data groups by executing the application program. The playback apparatus 400 comprises: the playback processing unit 412 operable to control the execution of the application program; the network IF unit 419 operable to obtain, from an external server including therein one or more alternative data groups, an alternative data group to replace part of the data groups; and the HDD unit 418 that stores therein correspondence information showing a correspondence between a storage location where on an internal recording medium the alternative data group is stored and a storage location where on the external recording medium the part of the data groups to be replaced. Here, at a time when the application program in execution reads a data group being referred to, the playback processing unit 412 (i) judges based on the correspondence information whether an alternative data group for replacing the data group being referred to exists on the internal recording medium, and (ii) specifies, as a data retrieve destination, a storage location of the alternative data group indicated by the correspondence information when the judgment is affirmative.