An image forming device prints out a data file including a data body, which is printed out, and additional data, which is not printed out. The additional data includes at least authentication data. The image forming device includes an identification entry unit, an operator authentication unit, and a print execution unit. The identification entry unit accepts an entry of the identification data of an operator. The operator authentication unit authenticates the identification data of the operator by the authentication data of the data file. The print execution unit prints out result data, according to whether the authenticated identification data is appropriate or inappropriate, along with the data body of the data file.