A screen saver having a function of managing a message for a computer system user, created by another user, and a method therefor are provided. The screen saver includes a screen saving portion for monitoring a state of a screen output to a display device provided in the computer system, an event detector for detecting an event input from an input device provided in the computer system, a password input portion for receiving a password from the user if the event detector detects the event, displaying the screen displayed immediately before the screen state is changed into the screen saving state if the password received from the user is identical with a prestored password, and changing the screen state into the screen saving state if not, and a message input portion for receiving a message from the user if the event detector detects an event, storing the message in a storage means provided in the computer system, and changing the screen state into a screen saving state. Therefore, when the computer system is in a screen protection mode and even when the user password of the user of the computer system is not known, another person can inform the user of a useful message using the computer system.