A lawn mower robot, comprising: an outer cover; an inner body accommodated 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, wherein the inner body comprises: a battery receiving portion opened downward from the bottom surface of the inner body, to receive and enclose the battery inside the inner body; and a battery cover mounted to cover a lower part of the battery receiving portion, wherein the waterproof unit comprises: a first sealing rib protruding downward from the bottom surface of the inner body into a rectangular box shape; a second sealing rib formed in a rectangular box shape and disposed outside the first sealing rib to be horizontally or longitudinally spaced apart from the first sealing rib; a sealing rib protruding upward along edges of the battery cover and inserted between the first sealing rib and the second sealing rib; and a battery sealer disposed at an inner side of the battery cover to be contactable with a lower end of the first sealing rib, so as to maintain airtightness between the battery receiving portion and the battery cover. an outer cover; an inner body accommodated 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, wherein the inner body comprises: a battery receiving portion opened downward from the bottom surface of the inner body, to receive and enclose the battery inside the inner body; and a battery cover mounted to cover a lower part of the battery receiving portion, wherein the waterproof unit comprises: a first sealing rib protruding downward from the bottom surface of the inner body into a rectangular box shape; a second sealing rib formed in a rectangular box shape and disposed outside the first sealing rib to be horizontally or longitudinally spaced apart from the first sealing rib; a sealing rib protruding upward along edges of the battery cover and inserted between the first sealing rib and the second sealing rib; and a battery sealer disposed at an inner side of the battery cover to be contactable with a lower end of the first sealing rib, so as to maintain airtightness between the battery receiving portion and the battery cover. a battery receiving portion opened downward from the bottom surface of the inner body, to receive and enclose the battery inside the inner body; and a battery cover mounted to cover a lower part of the battery receiving portion, wherein the waterproof unit comprises: a first sealing rib protruding downward from the bottom surface of the inner body into a rectangular box shape; a second sealing rib formed in a rectangular box shape and disposed outside the first sealing rib to be horizontally or longitudinally spaced apart from the first sealing rib; a sealing rib protruding upward along edges of the battery cover and inserted between the first sealing rib and the second sealing rib; and a battery sealer disposed at an inner side of the battery cover to be contactable with a lower end of the first sealing rib, so as to maintain airtightness between the battery receiving portion and the battery cover. a first sealing rib protruding downward from the bottom surface of the inner body into a rectangular box shape; a second sealing rib formed in a rectangular box shape and disposed outside the first sealing rib to be horizontally or longitudinally spaced apart from the first sealing rib; a sealing rib protruding upward along edges of the battery cover and inserted between the first sealing rib and the second sealing rib; and a battery sealer disposed at an inner side of the battery cover to be contactable with a lower end of the first sealing rib, so as to maintain airtightness between the battery receiving portion and the battery cover.