A lighting device configured for controlling a light radiation direction thereof, may include a housing provided with a light source; a lens unit provided in the housing, the lens unit being configured to concentrate the light generated from the light source; a length-variable unit mounted to the housing, the length-variable unit being configured so that a length thereof is changed, in a response to application of electricity thereto, in a direction in which the position of the lens unit is changed; and a controller configured to control a light radiation direction of the lens unit by setting a voltage of the electricity to be applied to the length-variable unit so that a length of the length-variable unit is changed according to a set voltage and the position of the lens unit is changed according to a change in the length of the length-variable unit.