Disclosed is a sound-absorbing material for an automobile, using foaming urethane foam to which carbon nano-tubes are applied, and a preparation method thereof. More particularly, disclosed is a sound-absorbing material for an automobile, which has excellent sound absorption and insulation performance while maintaining excellent flame retardancy, by increasing the ratio of open cells while uniformly maintaining the cell structure of the foam by adding carbon nano-tubes as a substitute for a portion of a flame retardant filler, and a preparation method thereof.