A heterogeneous storing server and a file storing method thereof are provided. The heterogeneous storing server has a file storing priority table which records different device type groups. The heterogeneous storing server determines the device type group to which a file belongs according to attributes of the file. The heterogeneous storing server stores the file into appropriate storing devices dynamically and adjusts the number of backups of the file in the storing devices dynamically according to a definition of the device type group.