An image forming apparatus includes: an internal authentication information storage unit that stores user authentication information relating to authentication for the image forming apparatus; an internal user authentication unit; an external authentication information storage unit that stores the user authentication information for external authentication, and a private IP address in association with one another for a plurality of URLs for external authentication; and a pseudo single sign-on unit that when it is determined that a redirection destination URL included in a response message transferred from a cloud server matches one of the stored plurality of URLs for external authentication, reads the user identification information for external authentication relating to the private IP address corresponding to a destination IP address included in a packet of the response message from the external authentication information storage unit, transmits the information for external authentication to the redirection destination URL, and performs the sign-on process.