An obstacle sensor includes a line light irradiating unit including a light-emitting unit, a light-emitting driving unit to drive the light-emitting unit, and a first conical mirror, an apex of which is disposed towards the light-emitting unit in a light irradiation direction of the light-emitting unit and which converts light emitted from the light-emitting unit into line light irradiated in all directions, and a reflected light receiving unit including a second conical mirror to condense light, that is irradiated from the first conical mirror and is then reflected from an obstacle, a lens, that is spaced from the apex of the second conical mirror by a predetermined distance and transmits the reflected light, an imaging unit to image the reflected light that passes through the lens, an image processing unit, and an obstacle sensing control unit.