Provided are an apparatus and a method for detecting an obstacle. The apparatus includes a light-emitting unit configured to emit a plane beam by converting a laser beam into the plane beam having a rectangular shape; a light reception unit configured to receive the laser beam which is emitted from the light-emitting unit and reflected from the obstacle; and a control unit configured to measure a distance to the obstacle by using the laser beam received in the light reception unit. Thus, an obstacle is detected by using the plane beam having a rectangular shape, so that the measurement range may be enlarged upwardly and downwardly.