If it is not a time zone of confidential mode and there is a print job to be executed, a print process is performed based on the print job, but if there is not a print job to be executed, non-confidential data stored in a HDD device is completely deleted. In the time zone of confidential mode, a determination is made as to whether or not there is non-confidential data, and after deleting the non-confidential data, a print process based on a print job to be executed is performed. The confidentiality of data is maintained without decreasing the processing efficiency of image formation.