A lawn mower robot includes an outer cover, an inner body positioned in the outer cover and having a plurality of wheels for traveling provided on both side surfaces thereof, a plurality of blades rotatably mounted on a bottom surface of the inner body to cut grass, electric devices mounted inside the inner body and including a battery, wheel driving motors, a blade driving motor, a plurality of ultrasonic sensor modules, rain sensors, a user interface (UI) module, and a universal serial bus (USB) port, and a waterproof unit to prevent penetration of water into the inner body or the electric devices, thereby improving waterproof performance.