The present disclosure relates to a lawn mower robot, including an inner body provided with casters and wheels for moving on both sides, respectively； a plurality of blades rotatably provided on a bottom surface of the inner body to cut grass； a drive motor mounted on the wheels, respectively, to independently drive the wheels； an outer cover configured to surround an outer side of the inner body, and mounted on the inner body to be movable in forward, backward, leftward and rightward directions with respect to the inner body when colliding with an obstacle； a plurality of ultrasonic sensors provided at a front side of the outer cover to sense an obstacle in front； and an ultrasonic guide unit formed to be recessed rearward from a front end portion of the outer cover so as to restrict a downward propagation angle of ultrasonic waves generated from the ultrasonic sensors.
