Image forming apparatus

An image forming apparatus is provided that is capable of preventing a print data from being leaked even where a user forgets to print out the print data with which an authentication data is attached. The image forming apparatus of the present invention has: a network interface receiving the print data, the authentication data, and an importance degree data; a hard disk drive storing the print data, the authentication data, and the importance degree data received by the network interface; an operation panel with which the user inputs the authentication data that is used to authenticate the print data; an authentication control unit comparing the authentication data stored in the hard disk drive with the authentication data input by the user; a control comprising a print processing unit controlling print processing of the print data stored in the hard disk drive based on the comparison result; and a time management unit measuring a time for which the print data is stored in the hard disk drive, wherein the control unit deletes the print data based on the importance degree data and the time for which the print data is stored in the hard disk drive.