A mobile device includes a file storage portion, a file reading portion, an index creating portion, an electric storage portion, an electric energy input/output portion, and an index creation determining portion. The file storage portion stores files. The file reading portion is capable of reading the contents of the files stored in the file storage portion. The index creating portion controls the file reading portion so as to read the contents of the files stored in the file storage portion and creates index data that can be used for searching of the contents of the files read by the file reading portion. The electric storage portion is capable of being charged/discharged. The electric energy input/output portion is capable of acquiring electric energy input from the electric storage portion and an external power source, and is capable of outputting electric energy to the electric storage portion, the file reading portion, and the index creating portion. The index creation determining portion permits the index creating portion to create the index data when an index creation condition that the electric energy input/output portion can acquire electric energy input from the external power source is satisfied, and does not permit the index creating portion to create the index data when the index creation condition is not satisfied.