Contents can be made public or private, when to be switched so, by designating a common file identifier before and after the switching. An information providing system reads a second file identifier related to a first file identifier, from a storage device (S25). The information providing system moves, in case it receives a request for making the contents public, the contents corresponding to the second file identifier read, to a public area, and moves, in case it receives a request for making the contents private, the same to a private area (S30). According to the stored place of the contents moved, the information providing system changes the second file identifier, and stores the same in the storage device in a correlation between the first file identifier received and the second file identifier changed (S35).