An electronic device comprises a distance detecting sensor for detecting a distance from a user to a target object, a light detecting sensor for detecting light intensity of external environment, a nine-axis sensor for detecting the user's motion, a control unit for determining whether the user is at high risk of vision loss based on the distance information output from the distance detecting sensor, the light intensity information output from the light detecting sensor, and the motion information output from the nine-axis sensor, and generating an alert command when it is determined that the user is at high risk of vision loss; and a vibrator for providing an alert based on the alert command output from a control unit.