An image forming apparatus performs a user authentication process and performs a private print process according to a request from an authenticated user. When the user requests interruption of the private print which is now performed or it is detected that the user has left a place near the image forming apparatus while the private print is being performed, the image forming apparatus interrupts the private print which is now performed and stores a print state at the interruption time. Further, the image forming apparatus performs a user authentication process and re-starts the private print which is interrupted in response to a re-start request from the authenticated user.