An image forming apparatus includes an apparatus casing installing an image formation section, an upper cover member that swingably covers and uncovers the apparatus casing, and an image reading unit supported by the apparatus casing via the upper cover member. A lock device is provided to maintain the upper cover member in a closed state. A unlock device is provided to unlock the lock device. A unlock operation section is displaced by an operator and activates the unlock device to operate when the lock device is unlocked. A unlock operation invalidating mechanism is provided to invalidate an unlock operation executed through the operation section by interrupting transmission of the displacement of the operation section to the lock device when unlock is prohibited