An image forming apparatus includes a display unit, a login information storage unit, a login information reception unit, a login authentication unit, an authorization limitation information storage unit, an execution instruction reception unit, a control unit and an execution permission determination unit. The authorization limitation information storage unit stores functions permitted to be executed by the logged-in user and a default user, who is a non-logged-in user. The control unit executes a function in accordance with an execution instruction received by the execution instruction reception unit. The execution permission determination unit determines whether the function indicated in the received execution instruction is a default function that is permitted to be executed by the default user, causes the control unit to execute the function if the function is the default function, and displays the login screen on the display unit if the function is not the default function.