In a personal authentication medium issuing apparatus, a main image information is input and whether a personal authentication medium on which synthesized image information having sub-information embedded in the main image information is checked or not is determined based on the state of the input main image information. Further, synthesized image information having sub-information embedded in an invisible state in the main image information which is set in a visible state is formed, a personal authentication medium is formed by printing the synthesized image information on a recording medium and the thus formed personal authentication media are sorted into personal authentication media determined to be completely formed and personal authentication media determined to require a checking process.