Without letting a user execute a cumbersome judgment of a version, an application program of the most suitable version is installed for data file automatically, thus an automatic activation of the application becomes possible. Firstly, a document file of a readout target is analyzed, a feature point as reserved word of macro instruction is extracted, and a version of an application suited for the document file is distinguished by an extracted feature point. Secondly, it is judged whether an application program of the version distinguished mentioned above is installed already. When found not being installed based on this judgment result, an application program of the version is newly installed.