The present disclosure relates to a lawn mower robot, including an inner body; an outer cover configured to surround an outer side of the inner body; a plurality of blades rotatably provided on a bottom surface of the inner body to cut grass; casters pivotably installed at both front sides of the inner body, respectively, to be pivotable about a rotation shaft; wheels rotatably mounted at both rear sides of the inner body, respectively; a driving unit configured to drive the wheels; and a sensor unit configured to sense whether or not the caster is lifted from the ground, wherein the sensor unit comprises a drop switch configured to sense the lowering of the caster when the caster is lowered in a state of being floated in the air.